A hippopotamus is sprayed with water on a hot summer day at Anna National Zoological Park in Chennai, India on April 26, 2017. (Photo by Arun Sankar/AFP Photo)

The 33rd All Women Lifeguard Tournament held at Sandy Hook Gateway National Recreation Area in Sandy Hook New Jersey. Wednesday, July 26th, 2017 (Photo by Anthony Causi)

Hot air balloons are prepared for a flight as others take off during an international hot air balloon festival at Maayan Harod National park in northern Israel September 30, 2015. (Photo by Baz Ratner/Reuters)

A hummingbird is photographed during the National Orchid Exhibition at the Jose Celestino Mutis Botanical Garden in Bogota, Colombia Septermber 20, 2018. Picture taken September 20, 2018. (Photo by Luisa Gonzalez/Reuters)

First prize. Taken over Bali Barat National Park, Denpasar, Bali. Made with a GoPro Hero 2 camera. (Photo by Capungaero)

Yawalapiti children play during the preparations for the celebration of “quarup”, a ritual held to honor in death a person of great importance to them, in the Xingu National Park, Mato Grosso State, May 7, 2012. (Photo by Ueslei Marcelino/Reuters)

The “Paolo Di Paolo: Lost World” exhibition presents more than 250 largely unseen images from the photographer’s archive. Di Paolo chronicled life in his country as an economic boom followed the destruction of the second world war. Although those were the years of la dolce vita he was an anti-paparazzo – he shunned the salacious and respected his subjects. The exhibition is at MAXXI, the National Museum of 21st Century Arts in Rome until 30 June. Here: Viareggio in 1959. (Photo by Paolo Di Paolo/National Museum of 21st Century Arts)

National Geographic photographer Steve Winter has spent most of his adult life shooting wild cats. Photo: A 14-month-old cub, cooling off in a pond, is riveted by a deer that appeared near the shore. Tigers are powerful swimmers; they can easily cross rivers four to five miles wide and have been known to swim distances of up to 18 miles. (Photo by Steve Winter/National Geographic)