Classes of Cenotes
In 1936 a sized based systems for cenotes was created and internationally agreed upon. Pit cenotes are just what they sound like, they have openings smaller than the body of water it leads to. Cylinder cenotes are those that have vertical walls, and basin cenotes have shallow water basins. The last class of cenotes is the cave cenote. These types of cenotes have horizontal entrances with various dry parts mixed with potentially flooded areas.
How are Cenotes Created
Cenotes are created by salt water and fresh water slowly dissolving rock that eventually digs a subsurface void. This void may or may not link to other larger cave systems and could even result in a cave in of the cenote's roof, exposing the void below.
The creation rates of these cenotes are increased when the cenotes aren't completely full with water. When the water levels drop, the process of dissolving the rock is increased from the sloshing waters. If the water has salt, such as ocean water, the rate of dissolution may be even greater.
Some cenotes are partly or fully collapsed. This will give the cenote the look of an open pool or a partial over hang, making it a common to actually have to crawl to get access to the water deep inside the cenote.
The most famous collection of cenotes in the Yucatan belongs to the Chicxulub Crater. The cenotes are formed here in a circular formation, outlining the crater that is believed to be the leftovers from the asteroid that killed the dinosaurs.
Most of the waters inside cenotes are amazingly clear due to fresh water rain filling and coursing through the underground channels. These natural formations can be anywhere from 160 to 330 feet below the normal water table, though there are a few cenotes that connect to one another.
For some reason, the cenotes that have collapsed roofs often have currents that travel faster than those in cenotes that are still covered by roofs. The number of cenotes in the Yucatan is actually a miracle of nature. There are nearly no rivers in the Yucatan and only a few lakes.
Most of the cities, new and old, have been built around these miracles of the nature with the idea being to have access to fresh water. The only other water source for the area is the Gulf of Mexico, which is all salt water.
The cenotes have been, and will be, one of the major attractions for the Yucatan as well as one of the deciding factors for the future survival of the environment.
To snorkel in cenotes check the Cenote Snorkeling Tour