The first dive centre to open in Tulum, in 1993, back when the cenotes were something you heard about from other divers rather than booked online. They were the ones who opened much of the cavern diving on this stretch of coast.
They run cenote and cavern dives, reef dives off Tulum itself, and snorkelling for people not carrying a certification. The shop is in the centre of town, on the corner of Centauro Sur and Sol Oriente.