I've never been on a cruise, but if I were to go on one I wouldn't carry anything other than my normal EDC stuff. Knife, flashlight, wallet, cellphone (which probably wouldn't work on a ship anyway), etc. Any ship-specific stuff that could help in an emergency would be too big to carry - a life raft, life preserver, cold water survival suit, shark repellant, flare gun, cutting torch, scuba tanks, semaphore flags, seawater purifier.

I would just relax, have a nice vacation, and pray that it wasn't my time to go. Walking around ship carrying all kinds of stuff like a Rambo/sherpa wouldn't be any fun at all.