Cenote Zapote (Hells Bells)
An hourglass-shaped sinkhole about 26 km west of Puerto Morelos, famous for the 'Hells Bells': bell-shaped calcite formations up to about 2 m long that hang from the walls between roughly 28 and 38 m. Research shows they form in a thin redoxcline just above the halocline, where a turbid sulfidic layer sits at about 35–37 m. The cenote bottoms out at around 54–55 m, and a tree trunk rises from the bed. It is a deep, dark dive rather than a classic shallow cavern tour.
depth: 0–40 m