A Russia fan shows her support prior to the 2018 FIFA World Cup Russia Group A match between Russia and Saudi Arabia at Luzhniki Stadium on June 14, 2018 in Moscow, Russia. (Photo by Lars Baron – FIFA/FIFA via Getty Images)

People wash in water from a broken water pipeline on the outskirts of Kolkata, India, March 30, 2016. (Photo by Rupak De Chowdhuri/Reuters)

Sumo wrestlers in their women's match at the 2021 Russian Sumo Championship at Ak Bars Wrestling Palace in Kazan, Russia on February 14, 2021. There are over 6,000 sumo wrestlers in Russia. (Photo by Yegor Aleyev/TASS)

The Rossiya (Russia) brig sails along the Neva River during a dress rehearsal of the 2021 Scarlet Sails Festival for school leavers in St Petersburg, Russia on June 25, 2021. (Photo by Peter Kovalev/TASS)

Russia's Maria Sharapova carries the torch during the opening ceremony of the 2014 Winter Olympics in Sochi, Russia, Friday, February 7, 2014. (Photo by Matt Dunham/Associated Press)

A Kashmiri Muslim woman balances on a water pipe before collecting water at Dasilpora village on March 22, 2018. World Water Day is held annually on 22 March as a means of focusing attention on the importance of freshwater and advocating for the sustainable management of freshwater resources. (Photo by Tauseef Mustafa/AFP Photo)

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.