I'm pretty sure that the S-18 would be a better choice if you went for the realism.
If you wanted to just have fun, pick the Porpoise or higher.
All subs have the same interior, I think,and even though the sub doesn't matter,
The slower the sub, the more time it takes and therefore, more realism.
That's what I think.
CAPTAIN RAMIUS
Always ready to leave the navy!