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.

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)

Giraffes doing the splits to get a drink of water from the watering hole at the Zimanga Private Game Reserve in South Africa on March 31, 2022. (Photo by Hendri Venter/Animal News Agency)

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)

German Oliver Struempfl competes to set a new world record in carrying one liter beer mugs over a distance of 40 m (131 ft 3 in) in Abensberg September 7, 2014. Struempfl carried 27 mugs over 40 meters to set a new record for the Guinness book of records. (Photo by Michael Dalder/Reuters)

Participants compete in a wife-carrying championship in Tapiobicske, Hungary, August 7, 2021. Some 40 Hungarian husbands, with their wives on their backs, clambered over rough terrain on Saturday in the nation's second wife-carrying contest. (Photo by Marton Monus/Reuters)

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)