Continuity mistake: At the end of the first attack by the destroyer - where she misses the U-boat and throws her bombs further away - the boatswain makes 22, then 23 strokes on the slate of the Control Centre,thus counting the number of depth charges used against the boat.A few seconds later, in a shot from another angle, with the slate in full view, we see only 22 strokes. (01:03:30)
Trivia: The movie is based on actual events and some of the characters have existed in real life. One of them, Pilgrim, took his own life after the book on which the movie is based was released.
Question: I know practically nothing about submarines, so this seemed a bit strange to me. When there's that huge storm, why do they keep staying at the surface, only going down for an hour at a time?