If you like the film, try the novel

If you enjoy this movie, I'd recommend the novel it was based on. Written by a former escort commander, the book has a very realistic feel to it, and explains a lot of the technical aspects of sub vs. destroyer warfare you don't get in the film. For example, the fact that the ASDIC device doesn't direct a beam directly beneath the ship, so when the sub is right under it, you can't find it. The beam has a silent "cone" that the destroyer captain uses to determine the depth of the sub (the farther away he is when you lose him, the deeper he must be). Also, the fact that depth charges sink more slowly the deeper they go, so it takes three times as long to get to twice as much depth.

The characters are a bit different, too, but not in a bad way. Frankly, they're more realistic, I think. The destroyer is a British vessel, and the captain is an experienced hand who is itching to try his lone ship against a sub to see if he can chalk up a kill on his own. He explains the advantages the sub has, and makes some good early moves to mitigate them. The sub commander is also an experienced captain who doesn't have as impressive a sinking record as other sub captains do, but then again, he's still alive and they aren't. He's an aristocrat, and disdains of Naziism not because he sees it as bad, but because it's beneath his social class. There's definitely a distinction in class in the boat, and it doesn't help his crew to deal with their situation. In one example, after a depth charge attack the captain asks his sonar operator if his hearing is okay, knowing that having the headphones on in an attack could hurt his eardrums. He doesn't ask out of any humanitarian concern; he asks because he needs the man's ears to function, and no more.

The ending is a bit different, with none of the cooperation you see in the film. I won't spoil it, though, if you want to read it.

All in all, if the film interested you, try the book. Good story, and very good information on the technicalities of sub vs. ship warfare.

Here's to the health of Cardinal Puff.