A market trader in Gaibandha in Bangladesh on September 25, 2019, surrounded by bottle gourd vegetables, which sell for around 3p ($ 0.04) each. (Photo by Solent News)

A 17ft anaconda which ate a pet dog seen blindfolded with a t-shirt is examined by Mano Bascoules in Montsinery, French Guiana. (Photo by Sebastien Bascoules/Barcroft Media/ABACAPress)

A contestant lies in a chili covered pool eating Chillies during a chili eating contest on July 8, 2018 in Ningxiang, Hunan Province of China. Citizen Tang Shuaihui ate 50 Chillies in one minute winning the contest. (Photo by VCG/Getty Images)

Auxiliary Territorial Service (ATS) plotters at work at Coastal Artillery Headquarters in Dover, December 1942. The Auxiliary Territorial Service was the women's branch of the British Army during the Second World War. It was formed on 9 September 1938, initially as a women's voluntary service, and existed until 1 February 1949, when it was merged into the Women's Royal Army Corps. The ATS had its roots in the Women's Auxiliary Army Corps (WAAC), which was formed in 1917 as a voluntary service. During the First World War its members served in a number of jobs including clerks, cooks, telephonists and waitresses. The WAAC was disbanded after four years in 1921. (Photo by Ted Dearberg/IWM/PA Wire)

Swiss rescue workers wheel a wounded person on a stretcher after two regional trains crashed head on near Granges-Pres-Marnand near Payerne in western Switzerland July 29, 2013. The two trains collided in the Swiss canton of Vaud on Monday evening, injuring about 40 people, four seriously, Swiss news agency ATS reported. There was no immediate report of any deaths in the crash. (Photo by Denis Balibouse/Reuters)

A fisherman caught a record-breaking 805lb Mako shark – and then barbecued and ate it with his friends. Joey Polk, 29, and his two cousins Earnie Polk, 43, and Kenny Peterson, 21, battled the 11ft predator for more than an hour before finally hauling it onto the beach. They normally tag and release their catches for conservation but were unable to resuscitate this one and instead made it the main course at a jumbo-sized family barbecue. (Photo by Joey Polk/Barcroft Media)

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.