Even better than shore story urban legends are the ones that supposedly happen at sea. One that popped into my head today was the "Legend of the SCRAM Switch Chicken Game".
"SCRAM Switch Chicken" was supposedly played by Reactor Operators, wherein they'd rotate the SCRAM Switch as far as they dared towards the "SCRAM" position (obviously without actually making the contacts) and leaving a pencil mark showing how far they'd gotten if they surpassed the old record. To make the game interesting, it would have to be done while the reactor was critical -- otherwise there was no risk. (You have to assume here that the EOOW was one of those officers who wanted to be "one of the guys".)
One story I heard about the game going too far involved a guy standing his last midwatch SRO before he got out of the Navy. This urban legend goes that he didn't much like his division mates, so he erased the old pencil mark and replaced it with one that was just past the "make" position of the switch. The story goes on that the next RO who tried the game underway got more than he bargained for when he tried to set a new record.
(Interestingly, a website of stories from the Enterprise has a similar account -- maybe that's where the submarine version came from.)
Similar Nuke Urban Legends tell of the dirty pictures put underneath various placards on the RPCP, along with the story of this message written on the back of isolation valve switch covers: "If you had a leak right now, you'd be screwed". (For the non-nukes out there, the only way to get the cover off was to take the handle off the switch.)
Midwatch SROs have a lot of time on their hands.