Duke Ellington, the film's composer, had to leave scoring the film to go on tour. Van Cleave and Frank Comstock were brought in not only to orchestrate the film but to finish the score and arrange the material. In the end, only five of Ellington's cues survived, with the rest being from the arrangers. Sadly, the master tapes to the score have been lost to time and the full extent of what Elliongton recorded that was not in the film will never be heard. In June 2016 Dragon's Domain Records released the score as heard in the film, but from monaural music stems, since the aforementioned master tapes no longer exist.
In its entry for this 1966 movie, the 2003 edition of Leonard Maltin's 'Movie and Video Guide' repeats a popular American terminological inexactitude by referring to the ocean liner as "HMS Queen Mary", thus implying that it was a warship at the time of the events depicted in the movie. The truth is that its designation has always been "RMS", traditionally meaning "Royal Mail Steamer" but nowadays sometimes taken to mean "Royal Mail Ship".
The Coast Guard cutter featured in the film displays the prototype of the modern racing stripe now used on all cutters. It was designed by Raymond Loewy / William Snaith and the final version was adopted servicewide on April 6, 1967.
It is somewhat ironic that Mark Brittain (Frank Sinatra) and Vic Rossiter (Anthony Franciosa) wore white covered hats while Erik Lauffnauer (Alf Kjellin wore a black covered hat. On a U-boat, the captain wore a white covered hat while the other officers wore a black covered hat.
Lauffnauer's quote of Winston Churchill, "The terrible 'If's' accumulate", is from Churchill's tome on WWI "The World Crisis", vol. 1, Chapter 11, page 255 (original edition).