There was once I took on the HMS Rodney in a Type VIIB with the deck gun...
It was part of a TF, and I spent my last eels on it. It was enough to stop her dead in the water, but not sink her.
So I dived, evaded the escorts and waited a full 24 (!) hours waiting for the rest of the TF to get far, far away, and hoping that the Rodney would sink. It didn't
So I surfaced about 6 km away, behind her stern so that her main guns couldn't be brought to bear. I started shelling her, managed quite a few hits once I got the range, and ran out of ammo!