Two large, almost circular cenotes ("eyes") connected by a 400-metre underwater passage in the jungle 50 km south of Tulum. The water is fresh, cold, and extraordinarily clear — visibility often exceeds 50 metres — and the limestone formations on the walls and roofs glow blue when light pours through. Snorkellers swim from one cenote to the other through the connecting passage, with a rope guide and a guide's flashlight overhead. Cave divers go much further into the side passages.
Entrance includes a brief safety briefing, life jackets and (optionally) snorkel gear. Visit early in the day before tour groups arrive; the experience is far better with fewer people in the water. Combine with a stop at the nearby Hidden Worlds park or with the Tulum ruins for a long day trip from Cancun.