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.

Royal sacred white oxen are offered food to consult the oracles during the Royal Ploughing Ceremony at the Royal Ground, Sanam Luang near the Grand Palace in Bangkok, Thailand, 09 May 2016. The ancient Brahmin rite is of great importance to the country's farmers. Thousands of farmers converge in Bangkok for the annual event, which is believed to assure a successful planting season and an abundance of crops. This year the sacred oxen ate paddy, sesame seeds, water and liquor which according to traditional soothsayers predicts that the country will have abundant food, sufficient water for agriculture as well as communication and foreign trade will improve leading to the prosperous economy. (Photo by Rungroj Yongrit/EPA)

In this Tuesday, September 12, 2017 photo, Amornrat Simapsaisan, a local shop manager, watches before she ate watermelon salad with bamboo worms, at Inspects in the Backyard restaurant, Bangkok, Thailand. Tucking into insects is nothing new in Thailand, where street vendors pushing carts of fried crickets and buttery silkworms have long fed locals and adventurous tourists alike. But bugs are now fine-dining at the Bangkok bistro aiming to revolutionize views of nature’s least-loved creatures and what you can do with them. She tucked in quite happily to her watermelon and cricket salad on a recent evening. “It’s tasty. It’s munchy”, she said. (Photo by Sakchai Lalit/AP Photo)

A participant of the “Zombie Takeover of Coney Island” acts like a zombie as he walks along Surf Avenue in Coney Island in the Brooklyn borough of New York, July 2, 2014. (Photo by Carlo Allegri/Reuters)

A makeup artist works on a model during the Tunis Fashion Week 2018 in Tunis, Tunisia, 12 May 2018. (Photo by Mohamed Messara/EPA/EFE)

Tourists photograph a red dear stag visiting a car park near Glen Coe on December 1, 2017 in Glen Coe,Scotland. On the first day of the meteorological calendar, the UK was experiencing slightly warmer temperatures today with weather forecasters indicating that the recent cold spell is almost over. Yesterday's snow across eastern parts of England is expected to melt away over the course Friday as temperatures start to rise. (Photo by Jeff J. Mitchell/Getty Images)

People pose for photos with scarecrow installations during the Scarecrow Art Festival at Huatuo Baicao Garden on November 22, 2025 in Bozhou, Anhui Province of China. (Photo by VCG/VCG via Getty Images)