Seconded, probabably one of the best World War II films made during the actual war.
1. It tries to be accurate (for a movie) and most of the events depicted did happen on subs. (Just not on one patrol.)
2. It actually tries to treat the Japanese as more than cardboard villians, with a brief discussion of how the militarists came to power.
3. Good special effects for a 1940’s film.
4. Top notch cast.
IMHO Cary Grant was one of the all time greats. 99% of the leading men in Hollywood today look like amateurs next to him.