The Enemy Below (1957)

Character mistake: About half-way into the movie the Captain asks for a fathometer reading and is told 150 fathoms. He preforms a mental calculation and says that it is 310 meters and over a thousand feet. In fact, 150 fathoms is 275 meters or 900 feet (1 fathom = 6 feet = 1.83 meters). (00:57:15 - 00:57:40)

Factual error: When the UBoat changes course, Andrews, operating the radar repeater, is immediately able to provide the bridge with the target's new course and speed. This would be impossible without extensive calculations and at least range and bearing plots once the target has steadied up on the new course, either figured on the scope screen or on a maneuvering board. One must remember that both vessels' courses and speeds must be taken into account when making computations, and the relative direction of a target's travel most often is not its true course.

Other mistake: Near the beginning of the movie, at the same time the ship makes radar contact, the sub acquires a signal on its oscillator. The sub captain thinks it's a false echo due to the rough seas. He so advises the next man that comes on duty but tells him that if the signal appears to get any closer, "you will awaken me immediately." The captain isn't awakened until the "dive" alarm sounds after the men in the conning tower make visual contact with the ship. Wouldn't the oscillator signal closing in on the sub have warned them long before they made visual contact?

Trivia: The scenes on the Haynes were filmed on an actual Buckley Class destroyer escort, the USS Whitehurst (DE 634). A great number of the Whitehurst crew act in the movie as the crew of the Haynes, with the commanding officer Lieutenant Commander Walter R. Smith playing the chief engineer (though on IMDB this role is credited to Robert Boon).

Trivia: The number of the (fictional) USS Haynes is DE-181. This number was actually used for the USS Straub - an actual Cannon Class escort destroyer.

Doctor: I guess you're finding the Sun kind of hard to take, after the North Atlantic.
Captain Murrell: Oh, it doesn't matter. It's always either too cold or too hot, wherever there's a war on.

Von Stolberg: We build 'em good in Germany, eh Heine?

Captain Murrell: I have no idea what he is, what he thinks. I don't want to know the man I'm... trying to destroy.