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.

St Mary's Cathedral is illuminated as part of a Christmas lights display in celebration of Christmas on December 19, 2014 in Sydney, Australia. (Photo by Brendon Thorne/Getty Images)

Musician St Vincent attends the 90th Annual Academy Awards at Hollywood & Highland Center on March 4, 2018 in Hollywood, California. (Photo by Carlo Allegri/Reuters)

The double compound eyes of a male St. Mark's fly (Bibio marci), submitted by Dr. David Maitland from Feltwell, UK. (Dr. David Maitland)

A man does physical exercise during sunset over the Finnish Gulf coast in St. Petersburg, Russia, Wednesday, April 14, 2021. (Photo by Dmitri Lovetsky/AP Photo)

Joy Corrigan attending the “BlacKkKlansman” premiere during the 71 st Cannes Film Festival at the Palais des Festivals on May 14, 2018 in Cannes, France. (Photo by Stephane Mahe/Reuters)

The sun rises over St Mary's Lighthouse in Whitley Bay on the Northumberland coast as a flock of Lapwing seabirds fly past on Wednesday, September 30, 2015. (Photo by Owen Humphreys/PA Wire)

The galactic core of the Milky Way glows brightly in the clear night sky above St Catherine?s Chapel at Abbotsbury in Dorset, UK on August 2, 2024. (Photo by Graham Hunt/Alamy Live News)