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.
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)
Suggested correction: He was in the sound room, not running sonar...given they were attacking a convoy, they wouldn't be running soar as that could be picked up by other ships.
That is not correct. The German U-boat is literally running passive sonar and detecting the destroyer with that. Active sonar, using a 'ping' sound that could be picked up by other ships, was rarely, if ever, used by German U-boats at all.
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)
Character mistake: After accurately depth charging U-571, the German destroyer crew suddenly turns out to be almost comically and unrealistically incompetent at the end of the movie. Not only do they barely hit U-571 with their guns, but they also can't keep up with the sub. But even with both submarine diesel engines running flank speed (of which U-571 only has one badly damaged engine operational), a common WWII destroyer would easily be twice as fast as a Type VII U-boat. The destroyer could swiftly close the distance and could either ram U-571 or cross the sub's wake to bring all its weapons to bear and make it more difficult to get hit by the sub. Of course the destroyer doesn't do that but stays perfectly in U-571's wake for an easy kill shot from its stern tube. In reality, it was considered an incredible feat to sink a destroyer with a torpedo, since they were agile at full speed, could easily dodge torpedoes and had shallow draft. This destroyer crew however, seems actively trying to get killed.
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: 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 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.
Suggested correction: This is explained in the film saying that the plane came from the destroyer on a recon mission.
If that is the explanation the film gives, it is a mistake in is own right. Firstly, destroyers did not carry recon planes, and secondly, recon planes are always equipped with floats, because they were launched from the ship by a catapult, but had to land on the water next to the ship to be lifted aboard by a crane.
Factual error: U-571 was sunk on January 8, 1944, by an Australian Sunderland. She was previously damaged by an Allied destroyer on March 22, 1943, but managed to come back to the base. All supply submarines (Type XIV or Type VIIF) were actually sunk by Allied planes or surface ships.
Suggested correction: They were on a course for Britain... they could have covered a good bit of ground before the plane flew over.
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)
Continuity mistake: In the start of the film Matthew McConaughey is sitting on a porch at a wedding reception smoking a cigar, in one shot he has a stub left then in the next it's a new one. (00:12:20)
Factual error: Several times the movie shows two torpedoes side by side, fired off simultaneously. This was not possible in German U-Boats, a simple timer prevented this and delayed firing the second or more torpedo by a few seconds. Torpedoes in WWII were prone to premature detonation and without this mechanism, one premature detonation could ignite a whole salvo, a significant risk of killing the sub that fired them.
Factual error: In reality, the planned boarding of the disabled sub would have been doomed to fail once the American and German subs met. Whenever German U-boats or ships met at sea, they were required to exchange a secret signal, usually consisting of a challenge-and-response using differently colored signal pistols. These signals changed daily and the Americans had no way of knowing this information.
Factual error: After the Americans have stormed the German sub, they find the Germans tried to destroy the Enigma code books by throwing them into the bilge water, which is just below the deckplates in the torpedo room. However, there was actually a lot of room for machinery and reserve torpedoes under the deckplates, which means that the torpedo room would have to be flooded by more than 3 feet deep to even reach the deckplates. This means the whole torpedo room would have been flooded with at least 6.000 gallons of water, rendering the boat likely completely unstable, unfit to dive and overflooding the batteries in the room next to it, which released poisonous chlorine gas when in contact with sea water. Not to mention that this much water could only have been caused by a major leak, but neither Germans or Americans seem to be particularly concerned by any leaks or by the amount of water in the boat.
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.
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)
