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The working title of the film was The Amphibian. The film closed with the following written acknowledgments and dedication: "To the Department of Defense and the Department of the Navy, for their cooperation in the filming of this motion picture, the producers wish to express their sincere gratitude. To the Navy Men of the Pacific Fleet, without whose help this picture could not have been made, our heartfelt thanks are extended. And to the divers of the Underwater Demolition Teams of the United States Amphibious Forces, whose story is told here, this picture is respectfully dedicated." Although the openings credits read: "And introducing Claire Kelly," Kelly had appeared in a bit role in The Best Things in Life Are Free and also in Scandal Incorporated, both released in 1956. Underwater Warrior was based upon the experiences of Cmdr. Francis D. Fane. A written prologue reads: "The unusual experiments in shark-infested waters were conducted in the Marshall Islands by Commander Francis D. Fane, U.S.N.R. Technical Advisor for this production, whose life and adventures inspired our picture." For more information about the Underwater Demolition Teams (UDT), see the entry above for the 1951 film The Frogmen.
Jon Lindbergh, son of famed aviator Charles Lindbergh, appears in a small role as a deck officer; this was his only film. Lindbergh spent three years as an ensign with the UDT and spent most of his life involved in underwater studies. The film was shot on location at San Clemente Island, Coronado, CA and in the Hawaiian and Marshall Islands. Hollywood Reporter production charts add Steve Litchell, Art Marshall, William Vaughn, Mike Steen, Arvid Nelson, Leo Needham, Mike Dugan and Thomas McBride to the cast, but their appearance in the released film has not been confirmed.