I heard a rumor once that submariners in the early days had their appendix taken out because of that possibility. I am guessing it was just one of those urban legends, but don't know for sure.
I know there was at least one case of a successful appendectomy performed by a Hospital Corpsman on board a sub, with help via radio (I think) from a doctor on some other ship. Not sure if that was during WW 2 or shortly after. Maybe it was in Reader’s Digest that I read about it.