[dread78645]

>> --unless you think you breached the pressure hull
Wouldn't that be obvious, quickly.

You might think so, but there's the battery compartment, sanitaries, and a sonar sphere where damage wouldn't be immediately obvious.

[Doohickey]

Seawater + H₂SO₄ = Hydrogen gas, and there is a hydrogen monitor and a CAMS suction in the battery well.

[antisocial]

I was aboard the USS Grenadier when she ran aground, I think it was in 1964. We were "snorkeling" in some shallow water when the stern planes locked up. It turned out that there was a bucket or something wedged in the stern plane.
The sonar dome was torn up and we had to go to the yards for repair. Pretty exciting stuff, since the USS Thresher had just gone down with all hands lost.