Cenote Angelita Underwater River

Cenote Angelita ('Little Angel') is a deep cenote located 17 km south of Tulum on Mexico's Yucatan Peninsula.

At approximately 30 meters depth, a dense layer of hydrogen sulfide gas forms an eerie cloud-like boundary that divides the cenote into two distinct worlds.

Above the cloud lies clear freshwater; below it, ancient saltwater fills the sinkhole down to its full depth of roughly 60 meters.

The hydrogen sulfide layer -- produced by bacterial decomposition of organic matter in the absence of oxygen -- appears as a thick, milky river complete with banks of dead leaves and fallen tree branches protruding from the cloud like a submerged forest.

The visual effect is so convincing that divers appear to be swimming above a flowing river within the cenote.

This phenomenon results from a halocline -- the boundary where freshwater and saltwater meet and do not mix due to density differences.

Organic debris (leaves, branches, humus) that falls into the cenote settles at this density boundary rather than sinking further, accumulating over centuries into what looks like a river bottom complete with log jams.

The hydrogen sulfide produced by anaerobic bacteria decomposing this organic layer creates the cloud effect.

The cenote is roughly 30 meters in diameter at the surface and opens into a vast underwater chamber below.

Its walls are sheer limestone, typical of Yucatan karst geology where the peninsula's porous limestone has been dissolved by acidic groundwater over millions of years, creating an interconnected system of thousands of cenotes and subterranean rivers.

Where to see it

A taste of where to see it. The full map, exact coordinates and the best timing for each spot live in the app.