On our one cruise, the ship (Norwegian Cruise Lines) had hand sanitizers everywhere. You had to use the stuff to get on the boat, before you entered any of the eating places, it was everywhere.

I don't know how they examine your checked bags, but if they found a knife in your carryon, or on your person, they took it away, gave you a receipt, and gave it back the last night of the cruise (apparently if you want to go postal and start slashing fellow passengers you have to wait 'til the last night to do it).

I would second the suggestion about flashlights. Something like my Surefire G2 shouldn't upset anyone, and it can get DARK outside if you are in the middle of the ocean if the lights on the boat go out...