A Playa del Carmen shop whose signature day is The Pit and Dos Ojos together — the first a shaft dropping past a hydrogen-sulphide cloud into darkness, the second a bright, shallow cavern system that is about as gentle an introduction to cenote diving as exists.
They also run the reef drifts off Playa and the bull-shark season. The shop is inland on Avenida 40; the published address could not be resolved to a precise point, so this is pinned on the centre of town — confirm the meeting place when you book.