Please note these comments are in the context of the fact that I never felt like playing submarines. (And aircraft carriers for that matter)
1- Submarines are not realistic. No WW2 era submarine can crash dive to 50 meters in 3 seconds.
2- No submarine can surface and dive in 3 seconds or less...
3- Submarines need to be reviewed before they are put into the main game.
4- For surface ships, there needs to be a way to see the bearing of the submarines once they dive, since it is not realistic to only say "impossible to hit" .OK, it may be impossible to hit. But once they are detected; any SONAR or ASDIC can detect and track their bearing...
5- How come no cruiser or DD except for a few have no means of sub-hunting gear ? Almost all cruisers and DD's had depth charges or ASROC / porcupine systems beginning from the mid 1930's...
6- The only way to avoid torpedo homing is to punch REPAIR in the game. However, shutting down engines and going into "silent cruise mode" for a surface ship should also disengage any homing... (Like hitting P to avoid detection by aircraft)
I hope these humble opinions of mine are of any help.