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)
Other mistake: The 'Fire Drill' will be a wet business for Lieutenant Werner the right side window on the car is open. At least you see a horizontal line almost halfway down on his side window. You see it when they meet the Bosun's Mate (time code 1). When they meet the men at their Fire Drill, (time code 2) it even looks as if Lt. Werner opens his window. (00:02:35 - 00:03:15)
Other mistake: During the heavy storm which lasts for 3 weeks, you can see clear blue sky above the U-Boat.
Other mistake: Prochnow drives to the boatyard in the opening scene - the drunken crew at the side of the road initiates him by pissing on the car as it passes. His passenger had just rolled down his window, when he saw the crew, but there is no evidence that he rolled it up before passing the crew. (00:04:55)DavidRTurner