A small Playa del Carmen operation diving both halves of what this coast offers: the cenotes inland — Dos Ojos, Chac Mool, the Pit — and the reef and drift dives off the town itself.
Cenote diving is not reef diving. The water is fresh, cold by Caribbean standards, and visibility is often a hundred metres; the cavern routes stay within sight of daylight, and anything beyond that is cave diving and needs its own certification. Guides here are required by law and by sense.
They publish a WhatsApp number as well as an email, which is how most of the coast actually takes bookings.