Revealing mistake: When the boat is supposedly surrounded by a swarm of flies, they're really just relatively few flies trapped between two panes of glass in front of the camera lens. Evidence: whenever the camera moves, the "swarm" moves with it against the background, and you can even see some of the insects walking on the surface of the glass.
Factual error: Sargent Nevins (Arthur Kennedy) is shown playing a pinball machine in the military rec room. When the camera turns to the play field of the machine, it is clear that this machine has flippers, and flipper buttons are visible on the side of the body. The movie takes place in 1943, but flippers didn't appear on pinball machines until 1947. (First machine to have flippers was Gottlieb's 'Humpty Dumpty.'. (00:37:30)ira