Character mistake: At the beginning of the movie, the German sub gets surprised and severely damaged by a destroyer. The sonar man first notices the enemy destroyer approaching, but only a short time before the destroyer is already literally on top of the sub. German sonar at the time had the capacity to detect ships up to more than 7 miles away, so the sonar man really had to be asleep at his sonar station not to notice the destroyer approaching. (00:03:40)
Factual error: In the last battle scene when you see shots of the German destroyer through the periscope the last one shot before it's blown up is really bad angling. The ship is far away but in the scope it's very close and the periscope (in order to get that camera angle) is 100 ft in the air.
Factual error: When the Americans are initially scrambling to figure out how the German submarine works, Rabbit opens a torpedo breech door, closes it and reports to Tyler "We have four fish, tubes are flooded." They are obviously not all flooded, otherwise Rabbit would just have flooded the compartment by opening the breech. (00:53:12)
Factual error: When the boarding party are eating dinner on SS-33 before the raid, some of their spanking-new, freshly pressed Kriegsmarine utility uniforms (strange in itself) have breast eagles on the left chest instead of the right. I've never seen any German Wehrmacht uniform with an eagle on the left.
Factual error: The submarine gets buzzed by a single engine German fighter. They are somewhere between the US coast and Greenland. The Germans had no aircraft carriers nor bases in the area. Since it was not a float plane how did the fighter get there? It could not possibly have flown the several thousand miles from continental Europe.
Factual error: At the beginning of the film the German commander is shown directing an attack using the periscope in the control room. German U-boats had two periscopes: a 'sky' scope (the one in the control room) used exclusively for searching the area directly above the boat prior to surfacing, and the 'attack' periscope located in the conning tower (turm). There'd be no sense in the commander using the sky scope - the attack scope had an integrated firing switch, much more stable view, smaller outline over water and better magnification. (00:03:00)
Factual error: The film is set during the war and there is a Toyota forklift driving around in one of the dock scenes.... (01:19:45)
Factual error: In the ship yard after the party, one of the navy crew is working on a sub and he is using a yellow plastic handled grinder. All tools in this era were metal handled. He's also wearing tennis shoes. (00:13:15)
Factual error: The language the American soldier and the secret-service officer use is grammatically correct German, but the pronunciation is very bad. No born German would ever be fooled by it.
Continuity mistake: Just after the sub surfaces and the crew arrives on the conning tower, the sub's deck is totally dry.
Factual error: The German supply U-boat couldn't have sunk the S-33 with a torpedo, as neither the Type XIV nor any other class of German supply sub was equipped with torpedoes (this would have meant less storage space for cargo).
Continuity mistake: When the S-33 is torpedoed, the boarding party members (including Tank) stand motionless, staring at the destruction in horror. Then Tank shouts "The scuttling charge!" and hurries towards the aft hatch to disable the explosives. Five seconds later, as the Chief throws a rope to Tyler, Tank can be seen standing motionless behind him, still staring at the destruction in horror. (00:48:30)
Factual error: At the beginning of the film the depth charge attack is shown rupturing a diesel fuel line in the engine room, which showers the fuel DOWN on the crew stationed there. In fact the fuel lines ran UNDER the deck plates and so a broken line could not shower fuel in that manner. (00:05:55)
Factual error: The "German" airplane which spots the crew before the destroyer scene is actually a Fiat G59 - a post-war two-seat training development of the G55 Centauro fighter. It is powered by a Rolls Royce Merlin engine.
Factual error: When the marine commando shows the sailor his "luggage" (the boxes of explosives) to be loaded onto the submarine, some of the boxes have orange Explosive B placards. Those are Dept. of Transportation placards. The D.O.T. didn't exist until 1966 and the placards were not used until later than that. (00:19:55)
Continuity mistake: Just after shooting the radio room on the German destroyer, U-571 submerges so quickly that the sailors do not manage to plug the gun. After a few moments when the boat goes from 180 to 200 meters there is a short shot from the above when we can clearly see that the gun is perfectly plugged. (01:13:30)
Factual error: Although the type of mission depicted in the movie did occur, it was not Americans that were known to do them. Canadian and British teams were specialized to do this mission.
Continuity mistake: During the first mission briefing, the commander is pointing to the map and you can clearly see the top secret photos of the enigma sitting by the manila envelope, but right after that shot he pulls the photos out of the envelope and hands them to people. (00:24:20)