Here are some things that need looked at in the sub class.

Subs are faster under water than on top of the water, so a speed increase should be included when at dive.

Snorkel, subs are more than capable of "breathing" at dive depth 1. If you can be seen, you should be able to breath.

Sonar is broken, I will successfully ping a sub, and get the no sub found message, all the while its tracking one.

Sonar avoidance buff is also broken, I have almost maxed out the sonar buff, and guys still see me just fine.

Dive time needs a slight buff, it is a submarine after all you should be able to stay under water for longer.

Limited weapons? Why no mines and other weapons subs have always been equipped with. The ability to deploy mines from torpedo tubes and from side launchers has been around for a long time. Why can subs not deploy mines?

Acoustic torpedos, why are these not included? They have been around since WWII. Shouldnt they be included?

Subs are fun, but they are a bit under balanced at the moment. 4 solid hits on a large ship should do substantial more damage than it currently does, especially with the short 2 min dive time.