Hi There,
I went with a dive group called "Scuba Caribe". Had a wonderful time. They service a lot of the resorts in Playa and Coz. They picked me up at my hotel and provided lunch. We did a trip to Coz { took the ferry}, we went off the beach in Playa and we went to the Cenotes. I would highly recomend doing a cenote dive. It was very cool. We had a small group { about 6} and the guide was very carefull/safe. The cenotes were crystal clear and beautiful. Have fun on your trip, wish I was going along.
Tom