I would definately recommend bringing a camera on the Cat Cruise. You're sure to get some get pictures...the Negril coast, people jumping off the cliffs, people swimming in the caves, people going off the slide, crazy limbo and dancing on the boat and awesome sunsets.
You definately don't need to swim...alot of folks just stay on the boat and watch.
Enjoy - we'll be back home in about 21 days and can't wait!
I have brought a really nice camera and lens and left it on the boat. I was sitting behind the driver so I just left it in a bag there. It's not like anyone could really steal it since there was nowhere to go. The last few trips I just brought my camera with underwater housing so I took it with me when we were swimming.
Take some zip lock bags to put stuff in if you are worried about it getting wet. My wife put the stuff in her beach bag which we carried on, but the bag did not get wet, so the zip locks were just extra protection. There is storage room under seats along the sides by the captain. We did not swim we just enjoyed watching everyone else, and have a few extra rum punches. Just got back, and now have 351 days left till our next trip to CN.