A shop a couple of streets back from the beach in Playa, diving the reef straight offshore and driving inland for the cenotes.
Playa's own diving is drift diving: you drop in, the current takes you north along the reef, and the boat follows your bubbles. It is the easiest diving on this coast and the reason a lot of people get certified here rather than somewhere harder. From November to March the bull sharks come in close to the beach, which is a different proposition entirely.