A tourist splashes water on the frozen Songhua River on December 18, 2023 in Harbin, Heilongjiang Province of China. The water immediately freezes into ice in the frigid air. (Photo by VCG/VCG via Getty Images)

A dead green sea turtle is collected from the beach at the Khor Kalba Conservation Reserve, in the city of Kalba, on the east coast of the United Arab Emirates, Tuesday, February 1, 2022. A staggering 75% of all dead green turtles and 57% of all loggerhead turtles in Sharjah had eaten marine debris, including plastic bags, bottle caps, rope and fishing nets, a new study published in the Marine Pollution Bulletin. The study seeks to document the damage and danger of the throwaway plastic that has surged in use around the world and in the UAE, along with other marine debris. (Photo by Kamran Jebreili/AP Photo)

The Tibetan night sky was captured in these beautiful images showing the stunning buildings and statues in the Himalayan mountains. Grey Chow, 33, traveled for two hours to get to the Spiti Valley to capture the starry backdrop along the isolated, deserted roads. The senior project engineer was able to take amazingly clear images thanks to the limited amount of pollution at the 4,500-foot (1371m) altitude. (Photo by Grey Chow/Caters News Agency)

This picture taken on January 17, 2019 shows jeepneys during rush hour in Manila, Philippines. Hand-painting custom decor on jeepneys adorned with images of everything from Batman to babies, as well as disco lights and chrome wheels, have for decades provided cheap transport for millions. But pollution and safety concerns have led to a modernisation programme, with jeepneys 15 years or older to be taken off the streets by 2020. (Photo by Noel Celis/AFP Photo)

An elephant sprays tourists with water in celebration of the Songkran Water Festival in Ayutthaya province, north of Bangkok, Thailand April 11, 2017. Trained elephants sprayed motorists and passers-by with water in Thailand's old capital city of Ayutthaya on Tuesday to welcome in the Buddhist New Year, known as “Songkran”. (Photo by Chaiwat Subprasom/Reuters)

A newly-hatched baby sea turtle makes its way into the Mediterranean Sea for the first time, as part of the Israeli Sea Turtle Rescue Center's conservation program, at a beach near Mikhmoret north of Tel Aviv, Israel September 9, 2019. Green turtles are endangered worldwide, the World Wildlife Fund says. Among other hazards, they are threatened by hunting, human encroachment on the beaches where they nest, and pollution of their feeding grounds offshore. According to the Israeli rescue center, only about 20 female green turtles nest along the Israeli Mediterranean coast during a breeding season that usually lasts from May until August. (Photo by Amir Cohen/Reuters)

A tree stands in a lake in Usingen near Frankfurt, Germany, Wednesday, March 22, 2023, the World Water Day. World Water Day was established in 1992 by the United Nations to spread awareness about the water condition all over the world. (Photo by Michael Probst/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.