Factual error: The movie used 3 "dive" commands and 3 blasts of the klaxon to dive. This is incorrect. The command to dive is repeated twice and the diving klaxon is sounded twice. Command to surface is 3 and 3.
Plot hole: In the movie the German sub is in the middle of the Atlantic about 1500 miles from the American coast the American submarine is an S-Class boat which had a top speed on the surface of 12 Knots even less underwater and it spent part of the trip submerged. This means that it would have taken them at least 5 or 6 days to reach the German Sub. This is 1942 There would have been dozens of other German subs a lot closer who could have come to their rescue.
Continuity mistake: When Mazzola dies, his eyes are initially open. The German captain pushes him away, and just before Mazzola's face goes out of camera he closes his eyes. In the next shot of him lying on his back on the floor, his eyes are open again.
Revealing mistake: When the German destroyer is hit by the torpedo at the end of the film it is seen to stop dead in the water upon the torpedo impact. In reality momentum would have carried the ship forward some distance after the explosion. A thousand or so tons of steel just does not stop on a dime unless it hits something like a mountainside.
Factual error: When the German "destroyer" is attacking, it drops a steady stream of depth charges. I reality, depth charge attacks were made by locating the sub on sonar and dropping a pattern of five or ten charges at a time when the escort ship was above the target. These were set for the estimated depth and would have gone off at roughly the same time.
Plot hole: The Americans disguise S-33 as a German Type VII U-boat to pose as the German resupply boat. This is a pretty bad idea, since all resupply boats are of the Type IXV and not Type VII. Of course in a severe storm the differences between types might go unnoticed, but the plan could not rely on that alone. In good visibility, any able German watchman would be able to spot the difference quickly.
Factual error: The American crew tries to fool the German destroyer by launching a corpse and debris through the torpedo tubes. However, at more than 150 meters depth this would have been pretty much suicide. The outer torpedo doors of a Type VII sub were not designed to be opened in depths exceeding 20 meters. At 150 meters, the crew probably would have been unable to open them in the first place, but even if they did the brutal water pressure would have likely severely destroyed the outer and inner torpedo doors and caused the submarine to be flooded and crushed in seconds.
Plot hole: At the beginning of the movie, the German commander sends a radio transmission with the damaged sub's position at "AL 85-32." The German Kriegsmarine divided up the Atlantic in grid squares like these, but "AL 85-32" means the damaged sub is just roughly 375 miles west of Ireland, but more than 2700 miles from the US east coast. There is no way on earth the Americans beat the Germans to this location, especially since the German supply sub is already en route. Funny enough considering the controversy about the movie, for this position the British would have been in perfect position to intercept.
Deliberate mistake: In the scene near the end of the movie when Trigger is in the bilge trying to stop the air leak, the concussion of an artillery shell fired from the destroyer shakes some pipes loose. The mistake is that one of the flanges visible on a section of pipe has no bolt holes, making it impossible to join that pipe to anything.
Other mistake: A German U-boat could dive in less than 30 seconds. By the time the boarding party even got to the conning tower the boat would already have been submerged.
Suggested correction: Just because it can, doesn't mean it has to. Not a mistake.
Yes mistake. The order to crash dive is heard. On a German sub the cry "Alarm!" always implied an order to crash dive as quickly as possible. A bit later the order to dive is given again. Practice on German subs was to open the quick-release vents as soon as the prompt "hatch latched" was given - in case of air attack often before that, meaning the vents were already open while crew members were still dropping through the hatch, resulting in the last guy getting an involuntary shower. True, the boat couldn't have dived in record time because they had no way in the ship, but still, at the very least the first thing the boarding party should have needed to do after taking the Central of U-571 should have been to close the vents and blow the tanks.
Continuity mistake: Mazzola has just been killed and when Tyler helps Tank, first he holds Tank using his left hand, then the next shot by his right.
