Factual error: When William Holden visits the Special Operations HQ for the first time a black vehicle is seen pulling in to the complex. The car is a 1948 Dodge or other Chrysler product which had not yet been manufactured.
Revealing mistake: Allison is wounded by a grenade fragment while disabling the Japanese 105's. But when his bloody shoulder is first seen, the blood stain is visibly too bright for real blood.
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: As the movie opens, the submarine is dispatching frogmen to acquire Japanese mines that are sonar-proof. The problem with this is that in order to locate mines by sonar, either the mines must make noises to be picked up by passive hydrophones, or the submarine has to start pinging with active sonar. Doing this makes the submarine vulnerable to any enemy listening in. I can't imagine a submarine venturing into a mined strait, announcing to one and all, "Here I am"..
Continuity mistake: According to one of the characters, the firing squad is drawn from the 3rd Battalion of the 701st Infantry Regiment, the same regiment as most of the other characters. However, all the members of the firing squad (except the officer and sergeant, who are credited characters seen elsewhere in the film) have "710" on their collar patches. This can be seen when the sergeant, who has "701" on his collar patches, is briefing them.
Continuity mistake: The flowers Sgt. Killian places in his helmet's netting change from fresh to wilted several times as the scenes change.
Factual error: A general arrives, but he does not have a star or stars on his epaulets; rather, he has eagles which belong to the grade of colonel.