Two children jumping through a water hydrant's shower on a New York street. They have come from a neighbouring co-educational playgroup organised by the city's Police Department. (Photo by Orlando/Getty Images). 1950

“Pilot whales are cetaceans belonging to the genus Globicephala. There are two extant species, the long-finned pilot whale (G. melas) and the short-finned pilot whale (G. macrorhynchus). The two are not readily distinguished at sea and analysis of the skulls is the best way to tell the difference between the two species. Between the two species, pilot whales range in waters nearly worldwide with long-finned pilot whales living in cooler waters and short-finned pilot whales living in warmer waters. Pilot whales are among the largest of the oceanic dolphins, exceeded in size only by the killer whale. They and other large members of the dolphin family are also known as blackfish”. – Wikipedia

Photo: Pilot whales swim in Loch Carron on May 20, 2011 in South Uist, Scotland. A major operation is underway to prevent up to 100 pilot whales from stranding on the rocky shoreline of Loch Carron on South Uist in the Western Isles. (Photo by Jeff J Mitchell/Getty Images)

Children fill plastic containers with water from a well on a street, close to a neighbourhood called “The Tank” in the slum of Petare in Caracas, Venezuela, March 17, 2016. Although their nation has one of the world's biggest hydroelectric dams and vast rivers like the fabled Orinoco, Venezuelans are still suffering water and power cuts most days. The problems with stuttering services have escalated in the last few weeks: yet another headache for the OPEC nation's 30 million people already reeling from recession, the world's highest inflation rate, and scarcities of basic goods. President Nicolas Maduro blames a drought, while the opposition blames government incompetence. (Photo by Carlos Garcia Rawlins/Reuters)

“Hippo Chase”. As we approached the camp the Selinda Reserve of northern Botswana our boat passed by a hippo resting in the water. I turned around to look back at the boat's wake and saw the hippo charging after us! The hippo must've been tired from an all-nighter because he was angry. He rose way up out of the water three times trying to chase our boat! He was coming at us with such force that he created a wake of his own. Photo location: Selinda Reserve of northern Botswana. (Photo and caption by Curtis Simmons/National Geographic Photo Contest)

These picture look like an artist has painted abstract patterns on canvas – but in fact they are natural rivers captured on camera. The spectacular rivers in Iceland's central highlands and southern parts originate from glaciers, which is why the water is a milky colour. They are shallow rivers and the water spreads quickly over a flat and sandy surface, creating random and beautiful patterns. Photographer Andrey Ermolaev from Moscow, Russia, flew 500ft above the unique sight in a small plane. (Photo by Andrey Ermolaev/Solent News)

Participants of the 79th edition of the annual Christmas swimming “Coupe de Noel” jump into the Lake Geneva, in Geneva, Switzerland, Sunday, December 17, 2017. More than 2000 men and women swam the 120 meters at the traditional Christmas swimming in Geneva where the water temperature was 6 degrees. (Photo by Martial Trezzini/EPA/EFE/Rex Features/Shutterstock)

Journalists interview a girl, member of the Cryophile amateurs winter swimmers club, after bathing in the ice waters of the Yenisei River, during the celebrations for the upcoming Christmas and New Year, in Krasnoyarsk, Russia, December 23, 2017. (Photo by Ilya Naymushin/Reuters)