As filed with the United States Securities and Exchange Commission on May 15, 2020

Registration No. 333-                      

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form S-3

Registration Statement

Under

The Securities Act of 1933

SEACOR Marine Holdings Inc.

(Exact name of registrant as specified in its charter)

12121 Wickchester Lane, Suite 500

Houston, Texas 77079

(346) 980-1700

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

John Gellert

President and Chief Executive Officer

SEACOR Marine Holdings Inc.

12121 Wickchester Lane, Suite 500

Houston, Texas 77079

(346) 980-1700

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public: From time to time after the effective date of this registration statement.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box:  ☐

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, please check the following box:  ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, please check the following box.  ☐

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, please check the following box.  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☒

CALCULATION OF REGISTRATION FEE

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with section 8(a) of the Securities Act or until the registration statement shall become effective on such date as the Commission acting pursuant to said section 8(a) may determine.

The information in this prospectus is not complete and may be changed. The selling stockholder may not sell the securities described herein until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell the securities described herein and neither we nor the selling stockholder are soliciting offers to buy such securities in any state where such offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED MAY 15, 2020

PROSPECTUS

900,000 Shares of Common Stock

This prospectus relates to an offer and sale of up 900,000 shares of common stock, par value $0.01 per share (“common stock”), of SEACOR Marine Holdings Inc., by the selling stockholder. The selling stockholder may offer shares of our common stock, from time to time, in a number of different ways and at varying prices. We will not receive any proceeds from the sale of common stock by the selling stockholder covered by this prospectus. We will bear all costs, expenses and fees in connection with the registration of the shares. The selling stockholder will bear all commissions and discounts, if any, attributable to the sale of common stock.

This prospectus provides you with a general description of the securities that our selling stockholder may offer. To the extent required by applicable law or regulation, each time securities are offered, the selling stockholder is required to provide this prospectus and, if required, a prospectus supplement. If a prospectus supplement is required, such prospectus supplement will contain more specific information about the offering and the terms of the securities being offered by our selling stockholder. A prospectus supplement may also add, update or change information contained in this prospectus.

The selling stockholder may offer and sell these securities to or through one or more underwriters, dealers and agents, or directly to purchasers, on a continuous or delayed basis. To the extent required, the specific terms of any securities the selling stockholder offers will be included in a supplement to this prospectus. Any such prospectus supplement will also describe the specific manner in which our selling stockholder will offer the securities.

Investing in our securities involves risks. You should carefully consider the risks described under “Risk Factors” on page 3 of this prospectus, as well as the other information contained or incorporated by reference in this prospectus and the applicable prospectus supplement, before making a decision to invest in our securities.

Our common stock is traded on The New York Stock Exchange (the “NYSE”) under the symbol “SMHI.” The last reported sales price of our common stock on the NYSE on May 14, 2020 was $1.82 per share.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities described herein or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is                 , 2020

TABLE OF CONTENTS

This prospectus is part of a registration statement that we have filed with the United States Securities and Exchange Commission, or the SEC. In making your investment decision, you should rely only on the information contained in this prospectus, any prospectus supplement and the documents that we incorporate by reference. We have not authorized anyone to provide you with any other information. If anyone provides you with different or inconsistent information, you should not rely on it. We are not making an offer of the securities described herein in any jurisdiction where the offer is not permitted.

You should not assume that the information contained in this prospectus or any prospectus supplement is accurate as of any date other than the date on the front of the respective document. You should not assume that the information contained in the documents incorporated by reference in this prospectus or any prospectus supplement is accurate as of any date other than the respective dates of those documents. Our business, financial condition, results of operations and prospects may have changed since those dates.

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we have filed with the SEC using a “shelf” registration or continuous offering process. Under this shelf registration process, the selling stockholder may, from time to time, sell up to 900,000 shares of our common stock that we have issued to the selling stockholder.

This prospectus generally describes SEACOR Marine Holdings Inc. and, provides you with a general description of the securities the selling stockholder may offer. To the extent required by applicable law, each time the selling stockholder sells common stock under this prospectus, the selling stockholder will provide you with this prospectus and, to the extent required, a prospectus supplement that will contain more information about the specific terms of the offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. Each such prospectus supplement (and any related free writing prospectus that we may authorize to be provided to you), if any, may also add, update or change information contained in this prospectus or in documents incorporated by reference into this prospectus. We urge you to carefully read this prospectus, any applicable prospectus supplement, if any, and any related free writing prospectus, together with the information incorporated herein by reference as described under the headings “Where You Can Find Additional Information” and “Documents Incorporated by Reference” before buying any of the securities being offered. We or the selling stockholder will deliver a prospectus supplement with this prospectus, to the extent appropriate, to update the information contained in this prospectus.

You should rely only on the information contained or incorporated by reference in this prospectus, any applicable prospectus supplement and any related free writing prospectus. We have not authorized anyone to provide you with any information in addition to or different from that contained in this prospectus, any applicable prospectus supplement and any related free writing prospectus. No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this prospectus, any applicable prospectus supplement or any related free writing prospectus that we may authorize to be provided to you. You must not rely on any unauthorized information or representation. This prospectus is an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. You should assume that the information in this prospectus, any applicable prospectus supplement or any related free writing prospectus is accurate only as of the date on the front of the document and that any information incorporated by reference is accurate only as of the date of the document incorporated by reference, regardless of the time of delivery of this prospectus, any applicable prospectus supplement or any related free writing prospectus, or any sale of a security.

This prospectus contains summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents. Copies of some of the documents referred to herein have been filed, will be filed or will be incorporated by reference as exhibits to the registration statement of which this prospectus is a part, and you may obtain copies of those documents as described below under the heading “Where You Can Find Additional Information.”

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This prospectus, including the documents incorporated by reference herein contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, (the “Securities Act”), and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Such forward-looking statements concern management’s expectations, strategic objectives, business prospects, anticipated economic performance and financial condition and other similar matters and involve significant known and unknown risks, uncertainties and other important factors that could cause the actual results, performance or achievements of results to differ materially from any future results, performance or achievements discussed or implied by such forward-looking statements. All of these forward-looking statements constitute the Company’s cautionary statements under the Private Securities Litigation Reform Act of 1995. The words “anticipate,” “estimate,” “expect,” “project,” “intend,” “believe,” “plan,” “target,” “forecast” and similar expressions are intended to identify forward-looking statements. Forward-looking statements speak only as of the date of the document in which they are made. The Company disclaims any obligation or undertaking to provide any updates or revisions to any forward-looking statement to reflect any change in the Company’s expectations or any change in events, conditions or circumstances on which the forward-looking statement is based. Risks that may affect forward-looking statements include, but are not necessarily limited to, those relating to:

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You should not place undue reliance on our forward-looking statements because the matters they describe are subject to known and unknown risks, uncertainties and other unpredictable factors, many of which are beyond our control. Our forward-looking statements are based on the information currently available to us and speak only as of the date on the cover of this prospectus. New risks and uncertainties arise from time to time, and it is impossible for us to predict these matters or how they may affect us. We have included important factors in the cautionary forward-looking statements included in this prospectus, particularly in the section of this prospectus entitled “Risk Factors,” which we believe over time, could cause our actual results, performance or achievements to differ from the anticipated results, performance or achievements that are expressed or implied by our forward-looking statements. We have no duty to, and do not intend to, update or revise the forward-looking statements in this prospectus after the date of this prospectus except to the extent required by the federal securities laws. You should consider all risks and uncertainties disclosed in our filings with the Securities and Exchange Commission, or the SEC, described in the sections of this prospectus entitled “Where You Can Find Additional Information” and “Documents Incorporated by Reference,” all of which are accessible on the SEC’s website at www.sec.gov.

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SUMMARY

This summary highlights selected information contained or incorporated by reference in this prospectus, and does not contain all of the information that you need to consider in making your investment decision. You should carefully read the entire prospectus, any applicable prospectus supplement, and any related free writing prospectus, including the risks of investing in our securities contained in the applicable prospectus supplement and any related free writing prospectus, and in the other documents that are incorporated by reference in this prospectus. You should also carefully read the information incorporated by reference in this prospectus, including our financial statements, and the exhibits to the registration statement of which this prospectus is a part.

Unless otherwise indicated or unless the context otherwise requires, references in this prospectus to the “Company,” “SEACOR Marine,” “SMHI,” “we,” “us,” or “our” are to SEACOR Marine Holdings Inc. and its subsidiaries.

Overview

The Company provides global marine and support transportation services to offshore oil, natural gas exploration and windfarm development and production facilities worldwide. As of March 31, 2020, the Company and its joint ventures operated a diverse fleet of 147 support and specialty vessels, of which 97 were owned or leased-in, 47 were joint-ventured, and three were managed on behalf of unaffiliated third-parties. The primary users of the Company’s services are major integrated oil companies, large independent oil and natural gas exploration and production companies and emerging independent companies, as well as windfarm operations and installation contractors.

The Company and its joint ventures operate and manage a diverse fleet of offshore support vessels that (i) deliver cargo and personnel to offshore installations including wind farms, (ii) handle anchors and mooring equipment required to tether rigs to the seabed, (iii) tow rigs and assist in placing them on location and moving them between regions, (iv) provide construction, well work-over, maintenance and decommissioning support and (v) carry and launch equipment used underwater in drilling and well installation, maintenance, inspection and repair. Additionally, the Company’s vessels provide accommodations for technicians and specialists, safety support and emergency response services.

Corporate Information

Our principal executive offices are located at 12121 Wickchester Lane, Suite 500, Houston, TX 77079, and our telephone number is (346) 980-1700. Additional information about us is available on our website at www.seacormarine.com. The information contained on or that may be obtained from our website is not, and shall not be deemed to be, a part of this prospectus. You can review filings we make with the SEC at its website at www.sec.gov, including our annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K and amendments to those reports electronically filed or furnished pursuant to Section 15(d) of the Exchange Act.

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The Offering

We are registering the resale of 900,000 shares of Common Stock issued pursuant to the MIPA (as defined below).

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RISK FACTORS

An investment in our securities involves a significant degree of risk. Before you invest in our securities you should carefully consider those risk factors included in our most recent annual report on Form 10-K and any subsequent quarterly reports on Form 10-Q and current reports on Form 8-K, which are incorporated herein by reference, and those risk factors that may be included in any applicable prospectus supplement, together with all of the other information included in this prospectus, any prospectus supplement and the documents we incorporate by reference, in evaluating an investment in our securities. If any of the risks discussed in the foregoing documents were to occur, our business, financial condition, results of operations and cash flows could be materially adversely affected. For more information on our SEC filings, please see the sections entitled “Where You Can Find Additional Information” and “Documents Incorporated by Reference.” Please also read the section entitled “Cautionary Statement Regarding Forward-Looking Statements.”

USE OF PROCEEDS

This prospectus relates to the offer and sale from time to time of 900,000 shares of common stock for the account of the selling stockholder referred to in this prospectus. We will not receive any proceeds from any sale of shares of common stock by the selling stockholder.

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DESCRIPTION OF CAPITAL STOCK

General

Our authorized capital stock consists of 60,000,000 shares of common stock, par value $0.01 per share, and 10,000,000 shares of undesignated preferred stock, $0.01 par value per share, of which no preferred shares are issued or outstanding.

The following summary description of our capital stock is based on the provisions of our third amended and restated certificate of incorporation (“Certificate of Incorporation”) and third amended and restated bylaws (“Bylaws”) and the applicable provisions of the Delaware General Corporation Law (“DGCL”). This information is qualified entirely by reference to the applicable provisions of our Certificate of Incorporation, Bylaws and the DGCL. For information on how to obtain copies of our Certificate of Incorporation and Bylaws, please see “Where You Can Find Additional Information” and “Documents Incorporated by Reference.”

Common Stock

As of May 4, 2020, there were 23,027,225 shares of our common stock outstanding. The holders of our common stock are entitled to the following rights.

Voting Rights

Holders of our common stock are entitled to one vote for each share held on all matters submitted to a vote of stockholders, and do not have cumulative voting rights. The common stock votes together as a single class. Directors will be elected by a plurality of the votes of the shares of common stock present in person or by proxy at a meeting of stockholders and voting for nominees in the election of directors. Except as otherwise provided in our Certificate of Incorporation or required by law, all matters to be voted on by our stockholders must be approved by a majority of the shares present in person or by proxy at a meeting of stockholders and entitled to vote on the subject matter.

Dividend Rights

Holders of common stock are entitled to receive proportionately any dividends as may be declared by our board of directors, subject to any preferential dividend rights of outstanding preferred stock.

Liquidation Rights

Upon our liquidation, dissolution or winding up, the holders of common stock are entitled to receive proportionately our net assets available after the payment of all debts and other liabilities and subject to the prior rights of any outstanding preferred stock.

Other Rights

Holders of common stock have no preemptive, subscription, redemption or other conversion rights and do not have any sinking fund provisions. The rights, preferences and privileges of holders of common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of preferred stock which we may designate and issue in the future.

Shares of our common stock are not convertible into any other shares of our capital stock.

Preferred Stock

As of May 4, 2020, there were no shares of our preferred stock outstanding.

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Pursuant to our Certificate of Incorporation, our board of directors has the authority, without further action by the stockholders (unless such stockholder action is required by applicable law or stock exchange listing rules), to designate and issue up to 10,000,000 shares of preferred stock in one or more series, to establish from time to time the number of shares to be included in each such series, to fix the designations, powers, preferences, privileges and relative participating, optional or special rights and the qualifications, limitations or restrictions thereof, including dividend rights, conversion rights, voting rights, terms of redemption and liquidation preferences, any or all of which may be greater than the rights of the common stock, and to increase or decrease the number of shares of any such series, but not below the number of shares of such series then outstanding.

The board of directors, without stockholder approval, can issue preferred stock with conversion or other rights that could adversely affect the voting power and other rights of the holders of common stock. Preferred stock could be issued quickly with terms designed to delay or prevent a change in control of our company or make removal of management more difficult. Additionally, the issuance of preferred stock may have the effect of decreasing the market price of the common stock and may adversely affect the voting power of holders of common stock and reduce the likelihood that common stockholders will receive dividend payments and payments upon liquidation.

Qualifications for Ownership

The U.S. cabotage laws impose certain restrictions on the ownership and operation of vessels in the U.S. coastwise trade (i.e., trade between points in the United States), including the transportation of cargo and passengers. These laws are principally contained in 46. U.S.C. § 50501 and 46 U.S.C. Chapter 551 and related regulations and are commonly referred to collectively as the “Jones Act.” Subject to limited exceptions, the Jones Act requires that vessels engaged in U.S. coastwise trade be built in the United States, registered under the U.S.-flag, manned by predominantly U.S. crews, and owned and operated by U.S. citizens within the meaning of the Jones Act. For purposes of the Jones Act, a corporation, for example, must satisfy the following requirement to be deemed a U.S. citizen: (i) the corporation must be organized under the laws of the United States or of a state, territory or possession thereof; (ii) each of the chief executive officer and the chairman of the board of directors of such corporation must be a U.S. citizen; (iii) no more than a minority of the number of directors of such corporation necessary to constitute a quorum for the transaction of business may be non-U.S. citizens; and (iv) at least 75% of each class or series of stock in such corporation must be owned by U.S. citizens within the meaning of the Jones Act.

Should the Company fail to comply with the U.S. citizenship requirements of the Jones Act, it would be prohibited from operating its U.S.-flag vessels in the U.S. coastwise trade during the period of such non-compliance. In addition, the Company could be subject to fines and its vessels could be subject to seizure and forfeiture for violations of the Jones Act and the related U.S. vessel documentation laws.

To facilitate compliance with the Jones Act, the Certificate of Incorporation and Bylaws: (i) limit (a) the aggregate percentage ownership by non-U.S. citizens of any class or series of the Company’s capital stock (including Common Stock) to 22.5% of the outstanding shares of each such class or series to ensure that ownership by non-U.S. citizens will not exceed the maximum percentage permitted by applicable maritime law (presently 25%) but authorize the Board of Directors, under certain circumstances, to increase the foregoing percentage to not more than 24% and (b) ownership of shares of any class or series of the Company’s capital stock by an individual non-U.S. citizen (and any other non-U.S. citizen whose ownership position would be aggregated with such non-U.S. citizen for purposes of the Jones Act) to not more than 4.9% of the outstanding shares of each such class or series; (ii) allow for the institution of a dual stock certification system to help determine such ownership; (iii) provide that any issuance or transfer of shares in excess of such permitted percentage shall be ineffective as against the Company and that neither the Company nor its transfer agent shall register such purported issuance or transfer of shares or be required to recognize the purported transferee or owner as a stockholder of the Company for any purpose whatsoever except to exercise the Company’s remedies under the Certificate of Incorporation; (iv) provide that any such excess shares shall not have any voting or

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dividend rights; (v) permit the Company to redeem or transfer to a charitable trust any such excess shares; and (vi) permit the Board of Directors to make such reasonable determinations as may be necessary to ascertain such ownership and implement such limitations. In addition, the Bylaws provide (w) that the number of non-U.S. citizen directors shall not exceed a minority of the number necessary to constitute a quorum for the transaction of business, (x) for an increase in the number of directors necessary to constitute a quorum when the number of non-U.S. citizen directors is equal to or greater than 50% of the number of directors present at a meeting, (y) that the President and the Chief Executive Officer of the Company must be a U.S. citizen and (z) that any non-U.S. citizen officer is restricted from acting in the absence or disability of the Chairman of the Board of Directors, the Chief Executive Officer or the President of the Company. For more information, see the Certificate of Incorporation and Bylaws.

Delaware Anti-Takeover Law and Provisions of our Certificate of Incorporation and Bylaws

Section 203 of the Delaware General Corporate Law.

We are subject to the provisions of Section 203 of the Delaware General Corporation Law (“Section 203”). In general, Section 203 prohibits a publicly held Delaware corporation from engaging in a “business combination” with an “interested stockholder” for a three-year period following the time that this stockholder becomes an interested stockholder, unless the business combination is approved in a prescribed manner. A “business combination” includes, among other things, a merger, asset or stock sale or other transaction resulting in a financial benefit to the interested stockholder. An “interested stockholder” is a person who owns 15% or more of the corporation’s outstanding stock, or an affiliate or associate of the corporation who did own 15% or more of the corporation’s voting stock within three years prior to the determination of interested stockholder status. Under Section 203, a business combination between a corporation and an interested stockholder is prohibited unless it satisfies one of the following conditions:

A Delaware corporation may opt out of Section 203 either with an express provision in its original certificate of incorporation or in an amendment to its certificate of incorporation or bylaws approved by its stockholders. However, we have not opted out, and do not currently intend to opt out, of this provision. The statute could prohibit or delay mergers or other takeover or change in control attempts and, accordingly, may discourage attempts to acquire us.

Certificate of Incorporation and Bylaws

Our Certificate of Incorporation and Bylaws contain provisions that may delay, defer or discourage another party from acquiring control of us. These provisions, which are summarized below, discourage coercive takeover practices or inadequate takeover bids. These provisions are designed to encourage persons seeking to acquire control of us to first negotiate with our board of directors, which we believe may result in an improvement of the terms of any such acquisition in favor of our stockholders. However, they also give our board of directors the power to discourage acquisitions that some stockholders may favor.

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Filling Vacancies on the Board of Directors.

In accordance with Article II, Section 12 of our Bylaws, any vacancy on our board of directors, however occurring, including a vacancy resulting from an increase in the size of our board of directors, may only be filled by the affirmative vote of a majority of our directors then in office even if less than a quorum. Any director appointed to fill a vacancy will hold office until the next election of directors or until their successors are duly elected and qualified.

Meetings of Stockholders.

Our Bylaws provide that only a majority of the members of our board of directors then in office or the Chairman of the board of directors or the President may call special meetings of the stockholders and only those matters set forth in the notice of the special meeting may be considered or acted upon at a special meeting of stockholders. Our Bylaws limit the business that may be conducted at an annual meeting of stockholders to those matters properly brought before the meeting.

Advance Notice Requirements

Our Bylaws establish an advance notice procedure for stockholders to make nominations of candidates for election as directors or to bring other business before an annual meeting of our stockholders. The Bylaws provide that any stockholder wishing to nominate persons for election as directors at, or bring other business before, an annual meeting must deliver to our secretary a written notice of the stockholder’s intention to do so. To be timely, the stockholder’s notice must be delivered to us not later than the 120th day nor earlier than the 150th day prior to the anniversary date of the preceding annual meeting. If there was no such prior annual meeting, then a stockholder’s notice must be delivered not earlier than the close of business on the 150th day nor later than the 120th day prior to the date which represents the second Tuesday in May of the current year. In the event that the date of the annual meeting is more than 25 days before or after such anniversary date, then, to be considered timely, notice by the stockholders must be received not later than the close of business on the 10th day following the date on which public announcement of the date of such meeting is first made by us.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is American Stock Transfer and Trust Company, LLC, 6201 15th Avenue, Brooklyn, NY 11219.

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SELLING STOCKHOLDER

This prospectus relates to the possible resale by a certain stockholder, who we refer to in this prospectus as the “selling stockholder,” of up to 900,000 shares of our common stock, as identified in the table below.

On March 20, 2020, pursuant to a membership interest purchase agreement (the “MIPA”) entered into among SEACOR LB Holdings LLC, an indirect wholly-owned subsidiary of the Company (the “Purchaser”), the Company, Montco Offshore, LLC (the “Seller”) and Lee Orgeron, the principal of the Seller (“Orgeron”), the Purchaser purchased the 28% minority equity interest in Falcon Global Holdings LLC (“Falcon Global Holdings”) held by the Seller (the “Equity Purchase”) in exchange for 900,000 shares of our common stock (the “Consideration Shares”). As a result of the transaction, the Company owns 100% of Falcon Global Holdings. The issuance of the Consideration Shares pursuant to the MIPA was made in reliance upon the exemption from registration provided under Section 4(a)(2) of the Securities Act. In determining that the issuance of the Consideration Shares qualified for an exemption under Section 4(a)(2), the Company relied on the following facts: (i) the Seller was an accredited investor or qualified institutional buyer, (ii) the Company did not use any form of general solicitation or advertising to offer the common stock and (iii) the investment intent of the Seller.

In connection with the MIPA, we entered into a registration rights agreement with the Seller and Orgeron, dated March 20, 2020 (the “Registration Rights Agreement”) and we are registering the Consideration Shares in accordance with our obligations under the Registration Rights Agreement.

The following table sets forth information with respect to the maximum number of shares of our common stock that may be offered from time to time by the selling shareholder under this prospectus. The selling stockholder identified below may currently hold or acquire at any time common stock in addition to those registered hereby. In addition, the selling stockholder identified below may sell, transfer, assign or otherwise dispose of some or all of their common stock pursuant to the safe harbor provided by Rule 144 under the Securities Act or in private placement transactions exempt from or not subject to the registration requirements of the Securities Act. Accordingly, we cannot give an estimate as to the amount of common stock that will be held by the selling stockholder upon termination of this offering. Information concerning the selling stockholder may change from time to time and, if necessary, we will supplement this prospectus accordingly.

To our knowledge, except as set forth herein, the selling stockholder has not, nor has had within the past three years, any position, office or other material relationship with us or any of our predecessors or affiliates, other than their ownership of our common stock. Because the selling stockholder may sell all or a portion of the common stock registered hereby, we cannot currently estimate the number or percentage of common stock that the selling stockholder will hold upon completion of the applicable offering.

The selling stockholder is not a broker-dealer registered under Section 15 of the Exchange Act, or an affiliate of a broker-dealer registered under Section 15 of the Exchange Act.

We have prepared the table and the related notes based on information supplied to us by the selling stockholder on or prior to May 14, 2020. We have not sought to verify such information. Other information about the selling stockholder may change over time.

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PLAN OF DISTRIBUTION

Selling Stockholder’s Plan of Distribution

We are registering the common stock held by the selling stockholder to permit the selling stockholder to resell these securities from time to time after the date of this prospectus. We will not receive any proceeds from the sale by the selling stockholder of the common stock covered by this prospectus. The selling stockholder may act independently of us in making decisions with respect to the timing, manner and size of each of their sales. These sales may be effected in one or more transactions including:

If the selling stockholder effects such transactions by selling common stock to or through underwriters, broker-dealers or agents, such underwriters, broker-dealers or agents may receive commissions in the form of discounts, concessions or commissions from the selling stockholder or commissions from purchasers of the common stock for whom they may act as agent or to whom they may sell as principal (which discounts, concessions or commissions as to particular underwriters, broker-dealers or agents may be in excess of those customary in the types of transactions involved). In connection with sales of the common stock or otherwise, the selling stockholder may enter into hedging transactions with broker-dealers, which may in turn engage in short sales of the common stock in the course of hedging in positions they assume. The selling stockholder may also sell common stock short and deliver common stock covered by this prospectus to close out short positions, and to return borrowed shares in connection with such short sales, provided that the short sales are made after the registration statement of which this prospectus forms a part is declared effective. The selling stockholder may also loan or pledge common stock to broker-dealers in connection with bona fide margin accounts secured by the common stock, which shares broker-dealers could in turn sell if the selling stockholder defaults in the performance of their respective secured obligations.

The selling stockholder may pledge or grant a security interest in some or all of common stock beneficially owned by them and, if they default in the performance of their secured obligations, the pledgees or secured parties may offer and sell the common stock from time to time pursuant to this prospectus. The selling stockholder also may transfer and donate the common stock in other circumstances in which case the transferees,

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donees or other successors in interest will be the selling beneficial owners for purposes of this prospectus. We will file an amendment or supplement to this prospectus, amending, if necessary, to include the pledgee, transferee or other successors in interest as selling stockholders under this prospectus on a list of selling stockholders.

Under the securities laws of some states, the common stock may be sold in such states only through registered or licensed brokers or dealers. In addition, in some states the common stock may not be sold unless such securities have been registered or qualified for sale in such state or an exemption from registration or qualification is available and is complied with.

There can be no assurance that the selling stockholder will sell any or all of the common stock registered pursuant to the registration statement of which this prospectus forms a part.

The selling stockholder and any other persons participating in such distribution will be subject to applicable provisions of the Securities Exchange Act of 1934, and the rules and regulations thereunder, including, without limitation, Regulation M of the Securities Exchange Act of 1934, which may limit the timing of purchases and sales of any of the common stock by the selling stockholder and any other participating persons. Regulation M may also restrict the ability of any person engaged in the distribution of the common stock to engage in market-making activities with respect to the common stock. All of the foregoing may affect the marketability of the common stock and the ability of any person or entity to engage in market-making activities with respect to the common stock.

We will pay all expenses of the registration of the common stock, however, the selling stockholder will pay all underwriting discounts and selling commissions, if any. We will indemnify the selling stockholder against liabilities, including liabilities under the Securities Act, in accordance with the Registration Rights Agreement, or the selling stockholder will be entitled to contribution in accordance with the terms of such agreements. We may be indemnified by the selling stockholder against civil liabilities, including liabilities under the Securities Act, that may arise from any written information furnished to us by the selling stockholder specifically for use in this prospectus, in accordance with the Registration Rights Agreement or, we may be entitled to contribution in accordance with the terms of such agreements.

Once sold under the registration statement of which this prospectus forms a part, the common stock held by the selling stockholder will be freely tradable by the purchasers of such securities, other than our affiliates.

To the extent required, this prospectus may be amended or supplemented from time to time to describe a specific plan of distribution. The place and time of delivery for the securities in respect of which this prospectus is delivered will be set forth in the accompanying prospectus supplements.

Any shares of common stock, covered by this prospectus that qualify for sale pursuant to Rule 144 of the Securities Act may be sold under Rule 144, rather than pursuant to this prospectus.

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LEGAL MATTERS

Unless otherwise indicated in the applicable prospectus supplement, our counsel, Milbank LLP, New York, New York, will pass upon certain legal matters in connection with the offered securities. Any underwriters, dealers or agents will be advised about other issues relating to any offering by their own legal counsel.

EXPERTS

The audited consolidated financial statements incorporated by reference in this prospectus and elsewhere in the registration statement have been so incorporated by reference in reliance upon the report of Grant Thornton LLP, independent registered public accountants, upon the authority of said firm as experts in accounting and auditing.

WHERE YOU CAN FIND ADDITIONAL INFORMATION

We file annual, quarterly and current reports, proxy statements and other information with the SEC. You may obtain copies of these reports, proxy statements and other documents at the SEC’s website, the address of which is http://www.sec.gov as well as on the Company’s website, the address of which is https://www.seacormarine.com/.

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DOCUMENTS INCORPORATED BY REFERENCE

The SEC allows us to “incorporate by reference” the information in certain documents that we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus, and the information that we subsequently file with the SEC will automatically update and supersede this information. This prospectus incorporates by reference the Company’s documents listed below and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act:

In addition, we incorporate by reference into this prospectus (i) all documents filed by us pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act subsequent to the date of this prospectus and before we have sold all of the common stock to which the prospectus relates or the offering is otherwise terminated and (ii) all documents filed by us pursuant to the Exchange Act after the date of the initial registration statement and prior to effectiveness of the registration statement.

To the extent that any information contained in any current report on Form 8-K, or any exhibit thereto, was furnished, rather than filed with, the SEC, that information or exhibit is specifically not incorporated by reference in this document.

You may obtain copies of these documents, other than exhibits, free of charge on our website, www.seacormarine.com, as soon as reasonably practicable after they have been filed with the SEC and through the SEC’s website, www.sec.gov. You may also obtain such documents by submitting a written request either to Investor Relations, SEACOR Marine Holdings Inc., 12121 Wickchester Lane, Suite 500, Houston, Texas 77079 or to InvestorRelations@seacormarine.com, or an oral request by calling the Company’s Investor Relations group at (346) 980-1700.

You should rely only on the information contained or incorporated by reference in this prospectus. We have not authorized anyone to provide you with information that is different from the information contained in this prospectus. This prospectus speaks only as of its date unless the information specifically indicates that another date applies.

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Common Stock

PROSPECTUS

            , 2020

Part II

Information Not Required in Prospectus

Item 14. Other Expenses of Issuance and Distribution

The following table sets forth the estimated fees and expenses, other than underwriting discounts and commissions, in connection with the issuance and distribution of the securities being registered hereby. With the exception of the SEC registration fee, all amounts set forth below are estimates. All of such expenses are being borne by the registrant unless otherwise indicated.

Item 15. Indemnification of Directors and Officers

Section 145 of the DGCL provides that a corporation may indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action, suit or proceeding whether civil, criminal, administrative or investigative (other than an action by or in the right of the corporation) by reason of the fact that he is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, against expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by him in connection with such action, suit or proceeding if he acted in good faith and in a manner he reasonably believed to be in or not opposed to the best interests of the corporation, and, with respect to any criminal action or proceeding, had no reasonable cause to believe his conduct was unlawful. Section 145 further provides that a corporation similarly may indemnify any such person serving in any such capacity who was or is a party or is threatened to be made a party to any threatened, pending or completed action or suit by or in the right of the corporation to procure a judgment in its favor by reason of the fact that he is or was a director, officer, employee or agent of the corporation or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, against expenses (including attorney’s fees) actually and reasonably incurred in connection with the defense or settlement of such action or suit if he acted in good faith and in a manner he reasonably believed to be in or not opposed to the best interests of the corporation and except that no indemnification shall be made in respect of any claim, issue or matter as to which such person shall have been adjudged to be liable to the corporation unless and only to the extent that the Delaware Court of Chancery or such other court in which such action or suit was brought shall determine upon application that, despite the adjudication of liability but in view of all of the circumstances of the case, such person is fairly and reasonably entitled to indemnity for such expenses which the Delaware Court of Chancery or such other court shall deem proper.

The Company’s Bylaws authorize the indemnification of its officers and directors, consistent with Section 145 of the DGCL, as amended. The Company has entered into indemnification agreements with each of its directors and executive officers. These agreements, among other things, require us to indemnify each director and executive officer to the fullest extent permitted by Delaware law, including indemnification of expenses such as attorneys’ fees, judgments, fines and settlement amounts incurred by the director or executive officer in any action or proceeding, including any action or proceeding by or in right of us, arising out of the person’s services as a director or executive officer.

Reference is made to Section 102(b)(7) of the DGCL, which enables a corporation in its original certificate of incorporation or an amendment thereto to eliminate or limit the personal liability of a director for violations of the director’s fiduciary duty, except (i) for any breach of the director’s duty of loyalty to the corporation or its

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stockholders, (ii) for acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law, (iii) pursuant to Section 174 of the DGCL, which provides for liability of directors for unlawful payments of dividends of unlawful stock purchase or redemptions or (iv) for any transaction from which a director derived an improper personal benefit. The Company’s Certificate of Incorporation provides for such exculpation from personal liability.

The Company maintains standard policies of insurance that provide coverage (i) to its directors and officers against loss rising from claims made by reason of breach of duty or other wrongful act and (ii) to the Company with respect to indemnification payments that it may make to such directors and officers.

Item 16. Exhibits

Item 17. Undertakings

(a) The undersigned registrant hereby undertakes:

(1) To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

(i) To include any prospectus required by Section 10(a)(3) of the Securities Act;

(ii) To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Commission pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20 percent change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement; and

(iii) To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement;

provided, however, that paragraphs (i), (ii) and (iii) above do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the registrant pursuant to Section 13 or Section 15(d) of the Exchange Act that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

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(2) That, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(3) To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

(4) That, for the purpose of determining liability under the Securities Act to any purchaser:

(i) Each prospectus filed by the registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and

(ii) Each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5) or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii) or (x) for the purpose of providing the information required by Section 10(a) of the Securities Act shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which the prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof; provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date.

(5) That, for the purpose of determining liability of the registrant under the Securities Act to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i) Any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

(ii) Any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant;

(iii) The portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

(iv) Any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

(6) That, for purposes of determining any liability under the Securities Act, each filing of the Registrant’s annual report pursuant to Section 13(a) or 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

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(7) Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, each registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

(8) For purposes of determining any liability under the Securities Act, the information omitted from the form of prospectus filed as part of this Registration Statement in reliance upon Rule 430A and contained in a form of prospectus filed by the registrant pursuant to Rule 424(b)(1) or (4) or 497(h) under the Securities Act shall be deemed to be part of this Registration Statement as of the time it was declared effective.

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SIGNATURES

Pursuant to the requirements of the Securities Act, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this Registration Statement on Form S-3 to be signed on its behalf by the undersigned, thereunto duly authorized in the City of New York, State of New York, on the 15^th day of May, 2020.

POWER OF ATTORNEY

Each person whose signature appears below constitutes and appoints John Gellert, Jesús Llorca, and Andrew H. Everett II and each of them, as his true and lawful attorneys-in-fact and agents, with full power of substitution and resubstitution, for him and in his name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this registration statement and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents full power and authority to do and perform each and every act and thing requisite or necessary to be done in connection therewith, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act, this registration statement has been signed by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

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Exhibit 5.1

55 Hudson Yards | New York, NY 10001-2163

T 212.530.5000

milbank.com

SEACOR Marine Holdings Inc.

12121 Wickchester Lane, Suite 500

Houston, TX 77079

Registration Statement on Form S-3

Ladies and Gentlemen:

This opinion is furnished to you in connection with a Registration Statement on Form S-3 (such registration statement, as amended or supplemented, is hereinafter referred to as the “Registration Statement”) filed with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”), for SEACOR Marine Holdings Inc., a Delaware corporation (the “Company”). The Registration Statement registers for resale 900,0000 shares of the Company’s common stock, par value $0.01 per share (the “Common Stock”) that were issued in connection with the membership interest purchase agreement dated as of March 20, 2020 (the “MIPA”) entered into among SEACOR LB Holdings LLC, an indirect wholly-owned subsidiary of the Company, the Company, Montco Offshore, LLC (“Montco Offshore”) and Lee Orgeron, the principal of Montco Offshore.

We are acting as counsel for the Company in connection with the registration of the Common Stock. We have examined the General Corporation Law of the State of Delaware (the “DGCL”), the Company’s Third Amended and Restated Certificate of Incorporation, as amended to the date hereof, the Company’s Third Amended and Restated Bylaws, as amended to the date hereof, the Registration Statement, the MIPA and the Registration Rights Agreement entered into in connection with the execution of the MIPA. We have also examined such other Company records, including resolutions of the Company’s board of directors, certificates, agreements and other documents, and such questions of law, as we have considered necessary or appropriate for the purposes of this opinion. In our examination, we have assumed the genuineness of all signatures, the legal capacity of all natural persons, the authenticity of all documents submitted to us as originals and the conformity with authentic original documents of all documents submitted to us as copies. As to various questions of fact material to our opinions expressed herein, we have, when relevant facts were not independently established, relied upon and assumed the accuracy and completion of certificates of the selling stockholders named in the Registration Statement and oral and written statements and representations of officers and representatives of the Company and public officials and statements and representations contained in the Registration Statement and other documents as we have deemed necessary as a basis for such opinions.

Based on and subject to the foregoing and assuming that (i) the Registration Statement and any amendments thereto (including any post-effective amendments) will have become effective and comply with all applicable laws and no stop order suspending the Registration Statement’s effectiveness will have been issued and remain in effect, in each case, at the time the Securities are offered or issued as contemplated by the Registration Statement, (ii) if required by applicable law or other regulations, a prospectus supplement will have been prepared and filed with the Commission describing the Securities offered thereby and any such prospectus supplement will at all relevant times comply with all applicable laws, (iii) the Company has timely filed all necessary reports pursuant to the Securities Exchange Act of 1934, as amended, which are incorporated into the Registration Statement by reference and (iv) all Securities will be sold in compliance with applicable federal and state securities laws and in the manner stated in the Registration Statement and the prospectus, if required by applicable law or regulations, we advise you that in our opinion the Common Stock has been duly authorized and is validly issued, fully paid and non-assessable.

The opinions above are subject to the issuance of any legally required consents, approvals, authorizations or orders of the Commission and any other regulatory authority. We express no opinion herein as to the laws of any state or jurisdiction other than the DGCL and the federal laws of the United States of America.

This opinion is based upon currently existing statutes, rules, regulations and judicial decisions, and we disclaim any obligation to advise you of any change in any of these sources of law or subsequent legal or factual developments which might affect any matters or opinions set forth herein.

We hereby consent to the filing of this opinion with the Commission as an exhibit to the Registration Statement in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act and to the use of our name therein and in the related prospectus under the caption “Legal Matters.” In giving such consent, we do not hereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission.

5/15/2020

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We have issued our report dated March 4, 2020 with respect to the consolidated financial statements of SEACOR Marine Holdings Inc. included in the Annual Report on Form 10-K for the year ended December 31, 2019, which is incorporated by reference in this Registration Statement. We consent to the incorporation by reference of the aforementioned report in this Registration Statement, and to the use of our name as it appears under the caption “Experts.”

/s/ GRANT THORNTON LLP

Houston, Texas

May 15, 2020