Croatia's Borna Sosa, left, fights for the ball with Brazil's Antony during the World Cup quarterfinal soccer match between Croatia and Brazil, at the Education City Stadium in Al Rayyan, Qatar, Friday, December 9, 2022. (Photo by Frank Augstein/AP Photo)

Members of the Unidos da Tijuca samba school parade at the “Opening of Carnival 2022” event, at the Cidade do Samba, in Rio de Janeiro, Brazil, 27 February 2022. The event is a preview of the parades of the Samba Schools of the Special Group, postponed to April due to the COVID-19 pandemic in Brazil. (Photo by Andre CoelhoEPA/EFE)

A Brazil soccer fan wearing contact lenses that mimic the Brazilian flag reacts as she watches her team play Germany in a World Cup semifinal game via live telecast inside the FIFA Fan Fest area on Copacabana beach in Rio de Janeiro, Brazil, Tuesday, July 8, 2014. (Photo by Leo Correa/AP Photo)

Fans gather to watch a FIFA World Cup Russia 2018 football match between Brazil and Costa Rica on a giant screen at Alzirao neighborhood in Rio de Janeiro, Brazil on June 22, 2018. (Photo by Carl De Souza/AFP Photo)

A spectator reacts after a Brazil Volleyball win during Paris 2024 Olympics in Women's Preliminary Round, Pool B Brazil vs Poland at South Paris Arena 1 in Paris, France on August 04, 2024. (Photo by Siphiwe Sibeko/Reuters)

Alligators and an egret stand on the banks of the Bento Gomes river next to the Transpantaneira road at the Pantanal wetlands near Pocone, Mato Grosso state, Brazil, Monday, September 14, 2020. A vast swath of the vital wetlands is burning in Brazil, sweeping across several national parks and obscuring the sun behind dense smoke. (Photo by Andre Penner/AP Photo)

A woman walks near a bus on fire as supporters of Brazil's President Jair Bolsonaro protest after supreme court justice Alexandre de Moraes ordered a temporary arrest warrant of indigenous leader Jose Acacio Serere Xavante for alleged anti-democratic acts, in Brasilia, Brazil on December 12, 2022. (Photo by Ueslei Marcelino/Reuters)

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.