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 man walks past a stranded public transport bus on a road flooded by heavy rains in Mumbai, India, August 5, 2016. (Photo by Shailesh Andrade/Reuters)

A woman feeds a pig in her yard during spring flood in the Belarus village of Snyadin near Pripyat river, some 300 km south of Minsk, on April 16, 2013. (Photo by Viktor Drachev/AFP Photo)

A man crosses a mud-covered trail carrying his wife on his back at a flooded Han River park in Seoul, South Korea, August 4, 2020. (Photo by Kim Hong-Ji/Reuters)

A damaged wooden garden house is seen amid a field of wheat following floods caused by heavy rainfalls, in Bad Bodendorf, Germany, July 18, 2021. (Photo by Wolfgang Rattay/Reuters)

A fruit vendor pushes his cart through a flooded street after a heavy rainfall in Lahore on September 21, 2021. (Photo by Arif Ali/AFP Photo)

Students attend the first day of in-person classes, at a flooded school due to high tide, in Macabebe, Pampanga province, Philippines on August 22, 2022. (Photo by Lisa Marie David/Reuters)

A woman walks through a flooded alleyway, after a heavy rain in Port-au-Prince, Haiti, Saturday, June 3, 2023. (Photo by Joseph Odelyn/AP Photo)