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 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 sloth peeks out from behind a door on a floating house in the “Lago do Janauari” near Manaus, Brazil, Tuesday, May 20, 2014. Manaus is one of the host cities for the 2014 World Cup in Brazil. (Photo by Felipe Dana/AP Photo)

Brazil's Victoria Chamorro failed to stop the ball during their women's classification 7th-8th place water polo match against China at the 2016 Summer Olympics in Rio de Janeiro, Brazil, Friday, August 19, 2016. (Photo by Sergei Grits/AP Photo)

Brazil's Kathellen in action with Australia's Alanna Kennedy during the Australia vs Brazil, Group C match at the FIFA Women's World Cup at Stade La Mosson Stadium on June 13th 2019 in Montpellier, France. (Photo by Eric Gaillard/Reuters)

#14 Kathellen of Brazil show her dejection after the 2019 FIFA Women's World Cup France Round Of 16 match between France and Brazil at Stade Oceane on June 23, 2019 in Le Havre, France. (Photo by Yves Herman/Reuters)

An indigenous woman looks on during the Terra Livre (Free Land) camp, a protest-camp to defend indigenous land and cultural rights that they say are threatened by the right-wing government of Brazil's President Jair Bolsonaro, in Brasilia, Brazil on April 4, 2022. (Photo by Adriano Machado/Reuters)