A cenote is a natural phenomenon, a sinkhole in the Earth’s surface. The Yucatan Peninsula in Mexico has an estimated 7,000 cenotes because it is primarily made up of porous limestone. For millions of years, rainfall slowly ate away at the limestone and a huge system of underground caves and caverns was formed. Many filled with water from rain or from the underground water table. When the roof of a water filled cave collapses, a cenote is born. The water found in a cenote may be fresh water, salt water, or both. Structurally it may be completely open, like a lake, almost completely closed with just a small opening at the top, or somewhere in between.

A tree stands in a lake in Usingen near Frankfurt, Germany, Wednesday, March 22, 2023, the World Water Day. World Water Day was established in 1992 by the United Nations to spread awareness about the water condition all over the world. (Photo by Michael Probst/AP Photo)

Actor Howard Coggins performs during the Living Spits Beauty and the Beast comedy at the Bristol Old Vic on December 9, 2020 in Bristol, England. Living Spit stars Howard Coggins and Stu McLoughlin will perform Beauty and the Beast in a series of live broadcasts and on stage shows at the Old Vic from December 18. (Photo by Matthew Horwood/Getty Images)

Boys and younger men from the Ilosvai Selymes Peter folk dance group pour buckets of cold water on a girl as they attend the traditional watering of local girls on Easter Monday in Komarovce, Velke Trakany, Slovakia on April 10, 2023. During Easter Holy Week, the ancient tradition of Easter sprinkling known as “watering of the girls” when Hungarian boys visit their female friends, recite poems, and pour water on them, and in exchange the girls offer the boys food and drink. (Photo by Robert Nemeti/Anadolu Agency via Getty Images)

An elephant sprays tourists with water in celebration of the Songkran Water Festival in Ayutthaya province, north of Bangkok, Thailand April 11, 2017. Trained elephants sprayed motorists and passers-by with water in Thailand's old capital city of Ayutthaya on Tuesday to welcome in the Buddhist New Year, known as “Songkran”. (Photo by Chaiwat Subprasom/Reuters)

Elephants spray tourists with water in celebration of the Songkran water festival in Thailand's Ayutthaya province, about 80 km (50 miles) north of Bangkok, April 9, 2014. (Photo by Rungroj Yongrit/EFE)

Ukrainians pour water on each other on a street in Lviv, Ukraine, 02 May 2016. The tradition of pouring water was an ancient spring ritual of cleansing on first Monday after Orthodox Easter. (Photo by Mykola Tys/EPA)

Boys play with water as they celebrate Myanmar's New Year Water Festival of Thingyan in Yangon, April 13, 2016. (Photo by Soe Zeya Tun/Reuters)