In the Spring of 1942, with German U-boats wreaking havoc with Allied convoys, a daring plan is hatched to capture a German Enigma encoding machine. So the Germans remain unaware of their loss, the plan is to disguise a US submarine as a German supply U-boat, rendezvous with a hunter-killer sub in the Atlantic and capture it. The plan works, but the American sub is sunk, and the nine-strong crew has to pilot the German boat home through hostile waters.
This should really be watched with The Patriot as an example of the American film industry rewriting history to suit itself; in reality, of course, it was a British crew which captured the Enigma machine. But aside from that, is U-571 a good adventure tale? Certainly it's good at capturing the claustrophobia and terror of depth-charge attacks and the violence of an Atlantic storm, though in some places the laws of physics seem to take a holiday as subs and torpedoes perform impossible tasks.
The real problem is that apart from the reliable Harvey Keitel, the cast is too lightweight to make you care about their fate. Stick with Wolfgang Petersen's Das Boot instead; it shared a production designer with U-571, and it's a submarine movie with a bit of humanity