Das Boot (1981) - Director's Cut.
9.5 out of 10.
It's outstanding. That movie was years ahead of its time.
It's only knock is that at over 200 minutes (Director's Cut), the movie just feels way too long.
And for a long time, nothing happens. But that's the point. The movie captures the boredom, fear and anticipation that can happen in a submarine.
The acting was magnificent.
I probably wouldn't watch it again because of how long it is, but one of the best films I've ever seen.