I quite enjoyed
Below as a claustrophobic horror film.
As for non-horror I've always liked
U571 and
The Land That Time Forgot. I also found the much derided
K-19 The Widowmaker to be a lot of fun.
Wes briefly mentioned it -
Crimson Tide - probably my favourite submarine film of all time. Great performances from Washington and Hackman that really wrack up the tension. I first saw it when i was staying in Hollywood for a week back in 95. Saw some fine films that week -
Species, Crimson Tide, Apollo 13 and
Braveheart, not to mention going to the world premier of
Under Siege 2, but thats another story. Proper Blockbusters - if i was there now i'd be stuck with superheroes and cartoons.
There are some enjoyable British WW2 sub movies that i own but also some creaky ones and i can never remember which are which.