In this July 29, 2021 file photo, the pillars of the massive Rosario-Victoria Bridge are exposed during a drought affecting the Parana River near Rosario, Argentina. At the port city of Santa Fe the river registered a level of 22 centimeters, the lowest in 50 years. (Photo by Victor Caivano/AP Photo/File)

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 river otter (lontra longicaudis) of 6-weeks-old looks in the mirror during a bath in the Animal Welfare Unit of the Zoo in Cali, Colombia, on October 22, 2019. The baby otter was found abandoned brought to the Cali Zoo for breeding, for its extensive experience in raising these species. According to the International Union for Conservation of Nature the river otter (lontra longicaudis) are in danger of extinction, because of mining, agriculture, pollution of rivers and housing construction in their habitat. (Photo by Luis Robayo/AFP Photo)

A fireman pulls a woman and her dog to shore, by a row of houseboats on the river Seine in Paris France, Wednesday June 1, 2016. The Seine River has overflowed embankments in Paris as floods hit or threaten cities and towns around France. (Photo by Jerome Delay/AP Photo)

A Sadhu or a Hindu holy man sits on the banks before taking a holy dip at Sangam, the confluence of the Ganges and Yamuna rivers with the mythical, invisible Saraswati river, during the “Maha Kumbh Mela”, or the Great Pitcher Festival, in Prayagraj, India, on January 13, 2025. (Photo by Adnan Abidi/Reuters)

A bucket of water is splashed on a woman during the Songkran water festival to celebrate the Thai New Year, in Prachinburi Province, Thailand, April 13, 2024. (Photo by Wason Wanichakorn/AP Photo)

Boys and younger men from the Ilosvai Selymes Peter folk dance group pour buckets of cold water on a girl as they attend the traditional watering of local girls on Easter Monday in Komarovce, Velke Trakany, Slovakia on April 10, 2023. During Easter Holy Week, the ancient tradition of Easter sprinkling known as “watering of the girls” when Hungarian boys visit their female friends, recite poems, and pour water on them, and in exchange the girls offer the boys food and drink. (Photo by Robert Nemeti/Anadolu Agency via Getty Images)

A dog swims as a resident navigates his boat in a neighbourhood flooded by the Purus river, which continues to rise from days of heavy rainfall in the region, in Boca do Acre, Amazonas state March 14, 2015. According the state civil defense, more than 20,000 people have been left homeless along the Purus river, where incessant rains have flooded the area and caused the river to burst their banks. (Photo by Bruno Kelly/Reuters)