A tourist splashes water on the frozen Songhua River on December 18, 2023 in Harbin, Heilongjiang Province of China. The water immediately freezes into ice in the frigid air. (Photo by VCG/VCG via Getty Images)

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.

Brides-to-be participate in the “Running of the Brides” race in a park in Bangkok, Thailand March 25, 2017. (Photo by Athit Perawongmetha/Reuters)

People enjoying the races on a wet day at Chester Racecourse on May 12, 2017 in Chester, England. (Photo by Alan Crowhurst/Getty Images)

A musher races with his dogs during a sled dog European Championship in Venek November 22, 2014. (Photo by Laszlo Balogh/Reuters)

Racing fans soak up the sunshine and dress to impress during Ladies Day at the Aintree Grand National meeting on April 8, 2011 in Aintree, England. Friday is traditionally Ladies day at the three-day meeting of the world famous Grand National, where fashion is as important as the racing.

Racing in the XOD class during day six of the Aberdeen Asset Management Cowes Week on August 11, 2011 in Cowes, England. (Photo by Alan Crowhurst/Getty Images)

A participant races in the Brompton World Championship in Bern, Switzerland October 21, 2018. (Photo by Stefan Wermuth/Reuters)