What Is a Cenote?
Sinkholes, flooded caves and sacred wells: a plain-English guide to the natural wonders of the Yucatán.
What is a cenote? The short answer
A cenote (say-NO-tay) is a natural sinkhole that opens onto groundwater. The Yucatán Peninsula sits on a thick slab of porous limestone with almost no surface rivers. Rainwater soaks straight into the rock, slowly dissolving it and carving caves that fill with fresh water. When the roof of one of those caves collapses, the water below is exposed: that opening is a cenote.
The word comes from the Yucatec Maya ts’ono’ot (often written dzonot), meaning a well or hole with water. The Yucatán has thousands of them, and for the ancient Maya they were both the main source of drinking water and sacred places linked to the underworld.
How cenotes form
- Limestone: the peninsula is an old seabed of limestone, lifted above sea level.
- Dissolving rock: rainwater picks up carbon dioxide and becomes slightly acidic, so over thousands of years it dissolves channels in the limestone.
- Caves: during ice ages, sea levels were much lower, the caves were dry, and stalactites and stalagmites grew inside them. As seas rose again, the caves flooded.
- Collapse: where the roof thins and falls in, light reaches the water and a cenote appears.
Those dry-era formations are why cave cenotes such as Taak Bi Ha are full of underwater stalactites: they could only have formed in air.
The four types of cenote
| Type | What it looks like | Examples near Tulum |
|---|---|---|
| Cave (underground) | Fully or mostly enclosed, reached by stairs or a small opening | Taak Bi Ha |
| Semi-open | Part of the roof has collapsed; part of the pool is under an overhang | Gran Cenote |
| Open | The roof has fully collapsed, like a natural pool or pond | Cenote Calavera, Cenote Cristal |
| Ancient / deep shaft | A deep, vertical well with water far below the rim | El Pit (diving only) |
Cave cenotes are the youngest in geological terms. Open cenotes are older, after the roof has completely fallen in. Our guide to cenotes near Tulum compares the best-known ones.
Why the water is so clear
Water filtering through limestone loses most of its sediment, and cave cenotes get little sunlight, so algae struggle to grow. Visibility can be remarkable. Many cenotes near the coast also have a halocline, where lighter fresh water floats on denser salt water that has seeped in from the sea. Divers see it as a shimmering, blurry layer.
The ring of cenotes and the Chicxulub crater
In northern Yucatán, many cenotes line up in a rough arc. Scientists link this "ring of cenotes" to the buried edge of the Chicxulub crater, left by the asteroid impact 66 million years ago, which is thought to have changed how the rock fractured and how water flows through it.
Underground rivers: the Sac Actun system
Many cenotes are connected underground. Near Tulum, the Sac Actun system, connected with Dos Ojos in 2018 according to INAH, is among the longest flooded cave systems ever mapped. That is why cave diving in the region is world famous, and why pollution in one spot can travel far.
How to visit a cenote responsibly
- Shower before you swim and skip sunscreen, repellent and lotions, even "biodegradable" ones, if the site asks.
- Don’t touch formations. Stalactites took thousands of years to form.
- Wear a life jacket if you are not a strong swimmer; most cenotes are deep.
- Respect the operators. Many cenotes are run by local ejidos or families; pay the entry, follow staff rules and bring cash.
- Never enter a cave beyond daylight without proper training and a guide.
Cenotes in Maya history
With almost no rivers, the Maya of the northern Yucatán built many of their towns around cenotes. Chichén Itzá means roughly "at the mouth of the well of the Itzá", and its Sacred Cenote was a place of pilgrimage and offerings: jade, gold, pottery and also human remains have been recovered from it. Cenotes were seen as entrances to Xibalbá, the underworld, and as homes of the rain god Chaak. Many are still considered sacred by Maya communities today, which is one more reason to visit respectfully.
Cenote vocabulary you’ll see on signs and tours
| Term | Meaning |
|---|---|
| Cavern | The part of a cave where daylight is still visible; where guided cavern dives stay |
| Cave | Beyond the reach of daylight; requires full cave-diving training |
| Halocline | The blurry boundary between fresh water on top and salt water below |
| Speleothem | Any cave formation: stalactites (hanging), stalagmites (rising), columns |
| Ejido | Community-owned land; many cenotes are run by ejidos |
| Colectivo | Shared minivan that runs along the highway; a cheap way to reach cenotes |
How to choose a cenote for your trip
- Want light and photos? Choose a cave cenote with a roof opening, and go when the sun is high.
- Travelling with kids? Choose an open or semi-open cenote with shallow areas and lifeguards, and bring life jackets.
- Want to see formations? A cave cenote such as Taak Bi Ha or a guided snorkel at Sac Actun.
- Want to dive? Book a certified cavern guide; sites such as Dos Ojos are classic first cavern dives.
- Short on time? Pick cenotes on the same road so you can visit two in one morning.
Protecting cenotes
Because the aquifer is connected, waste and chemicals that enter the ground in one place can reach cenotes far away. The same water is also the region’s drinking-water source. Use toilets where provided, take your rubbish with you, and support operators who limit numbers and enforce shower rules.
What is a cenote in simple terms?
A natural sinkhole where the ground has collapsed onto a pool of fresh groundwater, common on the Yucatán Peninsula in Mexico.
Can you swim in cenotes?
Yes, most cenotes open to visitors allow swimming. Expect deep water and follow the site’s rules on showers, sunscreen and life jackets.
Are cenotes fresh water or salt water?
Mostly fresh water. Near the coast, salt water can sit beneath the fresh water, separated by a layer called a halocline.
Why were cenotes sacred to the Maya?
They were the main source of fresh water in a land without rivers and were seen as entrances to Xibalba, the underworld. Offerings have been recovered from some, such as the Sacred Cenote at Chichén Itzá.
How many cenotes are there in Yucatán?
Thousands. Estimates vary widely, because many have never been formally surveyed.