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.

People cross a street against strong wind and heavy rainfall under the influence of Typhoon Haiyan, in Sanya, Hainan province November 10, 2013. One of the most powerful storms ever recorded killed at least 10,000 people in the central Philippines, a senior police official said on Sunday, with huge waves sweeping away entire coastal villages and devastating the region's main city. Despite weakening, the storm is likely to cause heavy rains, flooding, strong winds and mudslides as it makes its way north in the South China Sea. (Photo by Reuters/China Daily)

A surfer falls from their board a day after Tropical Storm Hilary swept through the area with large waves hitting south-facing beaches in Huntington Beach, California, on August 21, 2023. Tropical Storm Hilary drenched Southern California with record rainfall, shutting down schools, roads and businesses before edging in on Nevada on August 21, 2023. California Governor Gavin Newsom had declared a state of emergency over much of the typically dry area, where flash flood warnings remained in effect until this morning. (Photo by Frederic J. Brown/AFP Photo)

A young boy scoops water from a hand-dug well in the dry riverbed near Matinyani, in the semi-arid Kitui County in southeastern Kenya, 22 March 2015, the World Water Day. Residents of Kitui County and other arid and semi-arid areas of the country have been hard-hit by extremely poor rainfall this year while the government said in previous month that some 1.6 million people countrywide are facing acute starvation due to the drought and will need relief food over the next six months. Residents of Matinyani say they haven't seen a drop of rain in nearly four months. Thousands of Kenyans in rural areas walk tens of kilometers just to fetch water to drink and to be used in their homes. According to an estimate by UNESCO (United Nations Educational, Scientific and Cultural Organization), 17 million people lack access to safe water in Kenya, where the drought is a perennial problem. (Photo by Dai Kurokawa/EPA)

A girl looks on next to a damaged car buried in mud in an area heavily affected by torrential rains and flash floods in the village of Kamuchiri, near Mai Mahiu, on April 29, 2024. At least 45 people died when a dam burst its banks near a town in Kenya's Rift Valley, police said on April 29, 2024, as torrential rains and floods battered the country The disaster raises the total death toll over the March-May wet season in Kenya to more than 120 as heavier than usual rainfall pounds East Africa, compounded by the El Nino weather pattern. (Photo by Luis Tato/AFP Photo)

Galapagos – Rocking the Cradle: Four major ocean currents converge along the Galapagos archipelago, creating the conditions for an extraordinary diversity of animal life, April 25, 2016. The islands are home to at least 7,000 flora and fauna species, of which 97 percent of the reptiles, 80 percent of the land birds, 50 percent of the insects and 30 percent of the plants are endemic. (Photo by Thomas P. Peschak for National Geographic/World Press Photo)

Coaches of the North-East Express passenger train that derailed late Wednesday near Raghunathpur railroad station in Buxar district of Bihar state, India, Thursday, October 12, 2023. The train was on its way to Assam state from New Delhi. (Photo by Aftab Alam Siddiqui/AP Photo)

The sun sets behind artist Luke Jerram's “Floating Earth” at Pennington Flash on November 22, 2021 in Wigan, England. The floating Earth will hover over Pennington Flash for 10 days from November 19, as part of a celebration of Wigan and Leigh's watercourses and is the first time one of Jerram's globes has been floated on an open expanse of water. (Photo by Christopher Furlong/Getty Images)