Thank you for all of the helpful advice. I'm sure it has helped a lot of other people also.
Through this board and others we've come up with the following:
Ocho Rios, Jamaica - Tour with Peat Taylor
Caymans - Stingray Tour with Native Way
Cozumel - "Tarzan Tour" with Eagle Ray(a 4x4 jeep ride with lunch at the beach, time to snorkle and just be lazy at the beach!
Costa Maya - nothing booked but would like to see ruin site and will hire a taxi when we get there
I can't wait since it is only 10 degrees in NH at the moment, lower than that with the wind chill!