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.

A bodypainter uses UV paint to create electrifying masterpieces of stunning landscapes on models. John Poppletons vibrant Bodyscapes feature bright savannahs, lightning storms and vivid galaxies leaping from the bodies of his subjects. The artist, who lives in Wellsville in Utah, USA, uses a black light on his paintings to make them look as close to real life as possible. He predominantly uses female models and often paints across their backs to give him the largest surface area to work with. Here: “Bamboo Mist”. (Photo by John Poppleton/Caters News)

Under Exposed: Pekka Tuuri (Finland) – Great white shark, Isla Guadalupe, Mexico. “Isla Guadalupe is the world capital when it comes to observing great white sharks, but cage diving seriously limits the possibilities to take ‘fresh’ pictures. When I took this, the water close to the surface was quite milky, making photography very challenging. From out of the “mist”, I saw this great white shark lurking behind a school of fusiliers. I quickly focused on the shark and set a wide aperture to get focus blur on the fish, along with a fast shutter to avoid excessive motion blur”. (Photo by Pekka Tuuri/The Outdoor Photographer of the Year/The Guardian)

“The Lun-class ekranoplan (NATO reporting name Duck) was a ground effect vehicle (GEV) designed by Rostislav Evgenievich Alexeev and used by the Soviet and Russian navies from 1987 until sometime in the late 1990s. It “flew” using the lift generated by the ground effect of its large wings when close to the surface of the water – about four metres or less. Although they might look similar and/or have related technical characteristics, ekranoplans like the Lun are not aircraft, seaplanes, hovercraft, or hydrofoils – ground effect is a separate technology altogether. The International Maritime Organization classifies these vehicles as maritime ships. The name Lun comes from the Russian for harrier”. – Wikipedia (Photo by Igor113)

A model of the New Horizons spacecraft is seen at a live television program on NASA television celebrating the spacecraft's closest proximity to Pluto, at Johns Hopkins University Applied Physics Laboratory, site of the mission operations center, in Laurel, Maryland, USA, 14 July 2015. At approximately 7:49 am ET (11:49 am GMT), 14 July, New Horizons was scheduled to be as close to Pluto as the spacecraft will get; about 7,800 miles (12,500 kilometers) above the surface, following a journey of more than nine years and three billion miles. This is the first mission to the Pluto System and the Kuiper Belt. (Photo by Michael Reynolds/EPA)

Gray whale feeding at the surface and showing it's baleen. (Photo by Christopher Swann/Biosphoto)

On the Internet appeared the video, on which shows, according to the author of the video, as in the photos, which were taken by U.S. space probe MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging), American automatic interplanetary station (AWS) for the study of Mercury, on the surface of Mercury has been found an unusual object... (Photo by NASA)

Trees are reflected on the surface of a lake in the Okefenokee swamp lands in Georgia, USA on October 21, 2017. (Photo by Chris Moore/Solent News & Photo Agency)