Cenote - a natural freshwater jungle oasis found in the Yucatan Peninsula, Mexico
What is a Cenote?
Technically a cenote is simply a sinkhole; a place where the ceiling of an underlying cave fell in. The photo above was taken down inside the large collapse of the East Ojo at Dos Ojos cenote park.
The rubble pile of a collapse typically has very little soil. The specialized plants that grow here get nutrients from their fallen decomposed leaves and their roots split the rock to tap the cave water below.
The basins of some cenotes like the East Ojo may be filled with rubble (above) but others like Cenote Cristal south of Tulum (below) look very much like a normal pond.
Some cenotes are great swimming holes.
Local Maya and tourists come to cenotes like these to snorkel and swim in total sunshine. Their water-filled basins are usually teeming with fish like Sailfin Mollys and Mexican Tetras. A natural aquarium.
Thick polypropylene ropes that float are usually tied across these "open" cenotes so non-swimmers and kids have something to hang on to. This makes mom's job a little easier.
Partially closed cenotes have some areas in full sunshine and others under ceiling where less light penetrates. Here at Grand Cenote you can see the glow of a cavern diver's light in the dark area.
Semi-closed cenotes have overhanging ceilings with air space
The amount of sunlight that penetrates the water varies depending on water clarity and the strength of the sun. In the photo below, taken at the Grand Cenote, the sun has just gone behind some clouds.
When it re-emerges it's easy to see the difference. For cavern divers on SCUBA the sunlight is their primary reference to the cavern exit. To be safe divers need a qualified cavern guide and/or speciality training in cavern diving. Many area dive shops offer both tours and courses in cavern diving.
Not all cenotes have clear water. Tannic acid from fallen leaves can stain the water making it tea colored and warm water algae blooms can turn the water a cloudy green.
Below, seasonal cloudy water of Cenote Escondido in Tulum
Cavern snorkelers stay in the large open air space under the cave ceiling while cavern divers on SCUBA can explore where there is no air space. Sunlight should always be kept in sight. Dos Ojos below.
Dos Ojos Cenotes, some of the best
At Grand Cenote the main platform is the staging area for snorkeling and diving. Inside the cavern stalactites hang from the ceiling and penetrate the water. Submerged stalagmites rise from the floor.
Below, cavern divers get their equipment and buoyancy double checked by guides just before going down. Safety standards are very strict. It can be nerve racking to wait at the surface for their return.