The diving in Playa del Carmen is decent. Mainly drift diving. You can observe big schools of fish. Jacks, blue tangs, sergeant majors, angel fish, trigger fish, butterfly fish, grunts, drum fish, spade fish, parrot fish, big barracuda’s, trunk fish, snappers, file fish, are some of the fish that are pretty common in Playa del Carmen. With a bit of luck, you’ll bump into an eagle ray, sting rays, lobsters, king crabs, groupers, nurse sharks, flounders, turtles, tarpons, giant green morays, spotted eels and many more.
The bull shark season, starts in November and ends in February. http://www.youtube.com/watch?v=kkbRVSySf2I