We have been to Cozumel, Jamaica and Grand Cayman. Cozumel has good snorkeling or you can often go to the Playa del Carmen and see the ruins. Jamaica is my least favorite place - you need to be escorted there, do not venture out on your own. The shopping centers are all walled in for the tourists and heavily guarded. We took a tour and walked Dunn River Falls. It was beautiful, but, I'd prefer to stay on the ship.

Grand Cayman was wonderful - You must go to Stingray City, there are several options of swimming with the StingRays or going down into a submarine type of thing and watching a diver feed the rays. Also, it's fun to walk 7 mile beach and have lunch there at one of the hotels on the beach. I'd skip the Turtle Farm and Tour of Hell. The Turtle farm has a number of tanks full of large ocean Turtles and a gift shop and Hell is a convenience store where the proprietor wears a devil costume and has paraphanelia with Hell and Devil themes.