"Boats" is Navy slang for the rating of *Boatswain's Mate*. "Guns" is Navy slang for the rating of *Gunner's Mate*.
Patrick Wayne, John Wayne's son, has a small cameo - he plays the Australian Shore Patrol officer that breaks up the final fight.
Actor Mickey Simpson is sometimes mistakenly credited as the mate hit with a mop by Lee Marvin in the opening scene. It is not Simpson but Duke Green.
Actor John Qualen dubbed the voice of the sailor who yells "Man overboard!" in the opening scene, though it is not Qualen on-screen.
Although the character's full name is Michael Patrick Donovan, he is called "Mike" only twice in the movie, by LaFleur as he is throwing her off the balcony into the pond, and by Andre as he is trying to undercut Donovan. The character is called "Mr. Donovan" by Amelia and "Guns" by everyone else.
Ameilia asks the captain "to charter the Araner." That was the real name of John Ford's yacht, which is the yacht used in the movie.
During the scene where Amelia is wishing to "charter the Araner", Donovan states that he owns the Araner and a boat named the Inisfree. Inisfree is the name of the village in Ireland in which The Quiet Man, another John Wayne / John Ford film, takes place.
In a fight with Lee Marvin, John Wayne underestimated an uppercut. He crashed through a table and fell down. Director John Ford decided to leave the scene in the movie.
In the beginning, Gilhooley tells the captain who "shanghai'd" him that they were supposed to be at the island "on the 7th". Taking into account the time-line of the movie, ending on Christmas, that would make Donovan and Gilhooley's birthday as December 7th, the anniversary of the Japanese attack on Pearl Harbor.
In the movie Donovan and Gilhooley are supposed to share December 7th for their birthday. In real life, Mike Mazurki (Sgt. Monk Menkowicz) was born December 25, 1907.
Jack Warden, who played Elizabeth Allen's father, was only nine years her senior in real life.
This is the technically last movie that John Ford and John Wayne worked on together, although Wayne later provided the voice-over narration for Ford's documentary Chesty: A Tribute to a Legend.