Ronica
We didn't do a tour in Costa Maya and were disappointed that we didn't. The next time we go we plan to do the ruins. Everyone on our cruise who went enjoyed it. In Cozumel we went to Chankanaab Park and had a great time. Did the Sea Trek and the Sea Lion Swim there along with some snorkeling. Everyone that I know that did the Catamaran Sail and Snorkel also had a great time, but I can't comment from personal experience.
Darcy