EXHIBIT 21.1

McDERMOTT INTERNATIONAL, INC.

SIGNIFICANT SUBSIDIARIES OF THE REGISTRANT

YEAR ENDED DECEMBER 31, 2011

NAME OF COMPANY	JURISDICTION OF ORGANIZATION	PERCENTAGE OF OWNERSHIP INTEREST
McDermott International Investments Co., Inc.	Panama		100
J. Ray McDermott, S.A.	Panama		100
North Atlantic Vessel, Inc.	Panama		100
J. Ray McDermott (Aust.) Holding Pty Limited	Australia		100
McDermott Australia Pty Ltd	Australia		100
Hydro Marine Services, Inc.	Panama		100
McDermott Holdings (U.K.) Limited.	United Kingdom		100
McDermott Far East, Inc.	Panama		100
P. T. McDermott Indonesia.	Indonesia		75
McDermott Asia Pacific Pte. Ltd.	Singapore		100
J. Ray McDermott International, Inc.	Panama		100
McDermott Middle East, Inc.	Panama		100
McDermott Eastern Hemisphere, Ltd.	Mauritius		100
McDermott Arabia Holdings, Inc.	Saudi Arabia		6
McDermott Arabia Company Limited	Saudi Arabia		100
J. Ray McDermott (Luxemburg) S.ar.l.	Luxemburg		100
J. Ray Holdings, Inc.	Delaware		100
J. Ray McDermott Holdings, LLC.	Delaware		100
McDermott, Inc.	Delaware		100

The subsidiaries omitted from the foregoing list, considered in the aggregate as a single subsidiary, do not constitute a significant subsidiary.