What is at the bottom of a cenote?

Common things on the floor

• A cone of collapsed limestone from the old cave roof.
• Fine silt that clouds the water if disturbed.
• Fallen trees and leaves, which break down slowly.
• In some cenotes, a hazy sulfide cloud above the organic layer.

Archaeology and fossils

Divers have found Maya ceramics, jade, gold and human remains in sacred cenotes such as Chichén Itzá's, and Ice Age animal bones in flooded caves like Hoyo Negro. Such finds are protected by Mexican law; never take anything.

Can visitors see the bottom?

In shallow, clear cave cenotes you can see the floor while snorkeling. In deep open cenotes the bottom is usually out of sight, and only trained divers go down.

Sunken trees and a 'river' at Angelita

At Cenote Angelita near Tulum, divers pass through a hydrogen sulfide cloud that looks like an underground river, with dead tree branches poking through it (reported).

Caves full of bones

National Geographic has reported on Yucatán caves holding the bones of many people, some apparently thrown or left there, which locals consider haunted. Such sites are studied only by archaeologists.

How deep is the bottom?

It varies hugely. Many swimming cenotes are 10–40 m deep. Some go much deeper, and in Tulum-area cave cenotes the floor often slopes off into tunnels that run for kilometres. See our guide on how deep cenotes are.

Ice Age animals

In flooded caves near Tulum, divers have found bones of giant ground sloths, gomphotheres (elephant relatives), sabre-toothed cats and bears. These animals fell into dry pits during the last ice age, before the caves flooded. Hoyo Negro, where the Naia skeleton was found, is the most famous example.

Maya offerings

• Jade beads and carved pieces.
• Gold and copper discs and bells.
• Copal incense, rubber and pottery.
• Human remains in a few sacred cenotes like Chichén Itzá's.
• Smaller finds in cenotes such as Xlacah at Dzibilchaltún (reported).

Living things down there

• Blind cave fish and shrimp in dark passages.
• Bacteria living in the hydrogen sulfide layer.
• Roots of trees that reach down to the water.

Modern rubbish

Sadly, some cenotes near towns have trash, cars or construction debris on the floor. Cleanup groups and divers remove it. Never throw anything into a cenote, including coins.

Why the bottom looks dark or cloudy

• Light can't reach deep floors.
• Silt stirs up easily.
• Hydrogen sulfide or tannins from leaves can tint the water.

Halocline and hydrogen sulfide clouds

In deep cenotes close to the coast, salt water sits under the fresh water. Some cenotes also have a milky cloud of hydrogen sulfide where dead plants rot without oxygen. To divers it looks like a floor or a river, but it is really water layers, with more rock and sediment far below.

Why cenote bottoms are protected

Bones, pottery and fossils on the floor are part of Mexico's protected heritage. Touching or stirring the silt can destroy them and cloud the water for hours, so divers keep good buoyancy and never take anything.