“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)

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)

Nothing says Halloween like a jack-o'-lantern, but these professional carvings will blow your neighborhood pumpkin out of the water. (Photo by Frank C. Grace/Courtesy Jack-O-Lantern Spectacular)

A baby hippo swims under the water in its enclosure at Prague Zoo, Czech Republic, February 24, 2016. The baby was born on January 28, and is yet to be named. (Photo by David W. Cerny/Reuters)

A woman collects water from a stream outside the village of Tsemera in Ethiopia's northern Amhara region, February 13, 2016. (Photo by Katy Migiro/Reuters)

People wearing costumes attend the annual water-splashing festival to mark the New Year of the Dai minority in Jinghong, Yunnan province, April 13, 2015. (Photo by Reuters/China Daily)