A squatter argues with a police officer during an eviction at a settlement coined the “First of May Refugee Camp”, named for the date people moved on the land designated for a Petrobras refinery, in Itaguai, Rio de Janeiro state, Brazil, Thursday, July 1, 2021, amid the new coronavirus pandemic. (Photo by Silvia Izquierdo/AP 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.

Tom Nevins guts a feral pig sow during hunting on Silver Plains Station on October 8, 2011 outside of Coen, Australia. Feral pigs are recognised as environmental and agricultural pests reported to have a population of up to 23.5 million over around half of Australia. The Cooktown Hog Hunt is held annually with this year's hunting window open from registration at 2pm on Friday to the end of weigh in at 2pm on Sunday afternoon. (Photo by Mark Kolbe/Getty Images)

Emperor penguins gathered together to keep their chicks warm in these pictures. Marine scientist Frederique Oliver snapped the protective parents in Antarctica as they huddled against the huge winds.The adorable birds have to battle temperatures on -20 degrees Celsius as well as winds of up to 40 knots on the ice. (Photo by Frederique Oliver/Caters News)

On the second straight day of record-setting temperatures, Maddy Hacker is hoisted up by friend Jasmine Harper, both of McLean, Virgnia, as they attempt an acrobatic stunt in front of the U.S. Capitol in Washington, U.S., February 21, 2018. (Photo by Kevin Lamarque/Reuters)

A model is seen backstage before the Manish Arora Spring/Summer 2019 women's ready-to-wear collection show during Paris Fashion Week in Paris, France, September 27, 2018. (Photo by Stephane Mahe/Reuters)

A woman offers prayers at a temple during the Chinese New Year celebrations in Yokohama Chinatown, near Tokyo, Japan, 29 January 2025. The celebrations of the Chinese Lunar New Year, or Spring Festival, which falls on 29 January 2025, are held in Yokohama Chinatown, Japan's largest Chinatown. (Photo by Franck Robichon/EPA/EFE)