I totally LOVED snorkelling with the gigantic sea turtles at Akumal on the mainland. The schools of fish here were very cool, too. Seeing sea turtles in their natural environment is so much nicer than seeing them in captivity like you do on Grand Cayman.
The only reason I can't rate this excursion higher is that the snorkel mask provided here was total crap. My wife and I have snorkeled on cruises many times before... and never had problems with the equipment. But these masks were just bad compared to others we've used.
This was the best day of our two back-to-back cruises. LOVED it! The food was good, and the drinks were free. The pool was the right temperature, and the beach was nice. We just had a GREAT day here. I would do this again in a heartbeat.