Securities and Exchange Commission

Washington, D.C. 20549

Schedule 13G

(Rule 13d-102)

Information to be Included in Statements Filed Pursuant

to § 240.13d-1(b), (c) and (d) and Amendments Thereto Filed

Pursuant to § 240.13d-2

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 4)*

SEACOR Marine Holdings Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

78413P101

(CUSIP Number)

December 31, 2020

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

☐ Rule 13d-1(b)

☐ Rule 13d-1(c)

☒ Rule 13d-1(d)

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

(a) – (c) The responses of Mr. Fabrikant to Rows 5, 6, 7, 8, 9 and 11 of the cover page, which relate to the beneficial ownership of the Common Stock of the Issuer, are incorporated by reference.

As of December 31, 2020, Mr. Fabrikant beneficially owned an aggregate of 1,189,980 shares of Common Stock: (i) 485,232 shares that are owned directly, (ii) 93,606 shares, which Mr. Fabrikant has the right to acquire within 60 days upon the exercise of outstanding options granted by the Issuer, (iii) 360,414 shares owned by Fabrikant International Corporation, of which he is President, (iv) 65,459 shares owned by VSS Holding Corporation, of which he is President and sole stockholder, (v) 12,064 shares owned by the Sara J. Fabrikant 2012 GST Exempt Trust, of which he is a trustee, (vi) 14,406 shares owned by Sara Fabrikant, his wife, (vii) 19,097 shares owned by the Article Sixth Trust U/W/O Elaine Fabrikant FBO Eric Fabrikant, of which he is trustee, (viii) 60,324 shares owned by the Charles Fabrikant 2012 GST Exempt Trust, of which his wife is a trustee, (ix) 804 shares owned by the Harlan Saroken 2009 Family Trust, of which his wife is a trustee, (x) 804 shares owned by the Eric Fabrikant 2009 Family Trust, of which his wife is a trustee, (xi) 42,348 shares owned by the Charles Fabrikant 2009 Family Trust, of which he is a trustee, and (xii) 35,422 shares owned by Victoria Transport Corporation, of which he is President. Accordingly, as of December 31, 2020, Mr. Fabrikant beneficially owned approximately 5.1% of the Common Stock outstanding (based upon 23,435,254 shares of Common Stock outstanding as of October 30, 2020, as reported on the Issuer’s Form 10-Q for the quarterly period ended September 30, 2020).

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than 5 percent of the class of securities, check the following [ ].

Not applicable.

Not applicable.

Not applicable.

Not applicable.

Not applicable.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date: February 5, 2021