Cruising is a great escape from reality. No thinking, no worries. :grouphug:
Grand Cayman - swimming w/the sting rays is my favorite thing to do. It is a little unnerving when they swim between your legs, but it is a lot of fun. Also on GC, you NEED to buy rum cakes. Buy lots and lots of them - chocolate and regular are the best.
Cozumel - if you haven't any Mayan ruins, there should be several excursions that offer them. Chitchen Itza is a very extensive ruin (haven't been there). Tulum is also a good one (this is a must to do at least one. It is a loooooooong bus ride there and back, but worth it for how beautiful it is).