Gabriel Berendo, a businessman and car enthusiast, drives a casket converted into a car on Sunday May 31, 2020 in Cebu city, central Philippines as he goes around streets to remind residents to stay at home as lockdown measures to prevent the spread of the new coronavirus eases next week. (Photo by AP Photo/Stringer)

This picture taken on May 4, 2020 shows a gentoo penguin swimming in an enclosure at the Ocean Park theme park, which is currently closed due to the COVID-19 novel coronavirus, in Hong Kong. (Photo by Richard A. Brooks/AFP Photo)

Final-year student Alina Repkina prepares for a livestream of the Last Bell ceremony for school leavers at secondary school No 11 in Rostov-On-Don, Russia on May 30, 2020. It is the first time in Russia that such ceremonies have been held via video link due to the coronavirus lockdown restrictions. (Photo by Valery Matytsin/TASS)

Ride operator Van Mai wears a face mask against the spread of the coronavirus while working at the Playland amusement park at the Pacific National Exhibition, in Vancouver, British Columbia, Friday, July 10, 2020. (Photo by Darryl Dyck/The Canadian Press via AP Photo)

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.

Alluvial Fan, China. A vast alluvial fan blossoms across the desolate landscape between the Kunlun and Altun mountain ranges that form the southern border of the Taklimakan Desert in China’s XinJiang Province. Image taken by the ASTER instrument on NASA’s Terra satellite on May 2nd, 2002. (Photo by NASA/GSFC/USGS EROS Data Center)

A house built on a rock on the river Drina is seen near the western Serbian town of Bajina Basta, about 160km (99 miles) from the capital Belgrade May 22, 2013. The house was built in 1968 by a group of young men who decided that the rock on the river was an ideal place for a tiny shelter, according to the house's co-owner, who was among those involved in its construction. (Photo by Marko Djurica/Reuters)

Mug shot of William Stanley Moore, 1 May 1925, Central Police Station, Sydney. This picture appears in the Photo Supplement to the NSW Police Gazette, 28 July, 1926 captioned: “Opium dealer. Operates with large quantities of faked opium and cocaine. A wharf labourer; associates with water front thieves and drug traders”. (Photo by NSW Police Forensic Photography Archive, Justice & Police Museum, Histiric Houses Trust of NSW)