Malian workers haul out a boat they use to carry sand collected from the river bed during a routine maintenance on October 7, 2018, in the port of Bamako. Increasing construction in the Malian capital has boosted the demand for bricks made out of high-quality Niger River sand. (Photo by Michele Cattani/AFP Photo)

Cha Huilan, a 40-year old Lisu woman, and her daughter leave Lazimi village with a zipline across the Nu River in Nujiang Lisu Autonomous Prefecture in Yunnan province, China, March 24, 2018. Chinese mountain villagers, cut off from shops and churches by a raging river, use a zipline to cross its violent rapids and jagged rocks. (Photo by Aly Song/Reuters)

A young arab boy, armed with a rifle and a knife, in the Aden Protectorate near Yemen. (Photo by Richards/Fox Photos/Getty Images). February 1938

The Lady Boys of Bangkok have fun at the Meadows August 1, 2006 in Edinburgh, Scotland. (Photo by Jeff J Mitchell/Getty Images)

A British policewoman chasing after a group of naked street boys by the Serpentine in Hyde Park, London. (Photo by Reg Speller/Getty Images). 1926

In this May 24, 2016 photo, a young boy descends the Qullqip'unqu mountain looking out at the tens of thousands of pilgrims gathered to celebrate the three-day festival Qoyllur Rit’i, translated from the Quechua language as Snow Star, in the Andean Sinakara Valley, in Peru's Cusco region. The celebration that mixes Catholic and indigenous beliefs honors Jesus as well as the area’s glacier, which is considered sacred among some indigenous people. While the native celebration is far older, the Christian part of the ritual stretches back to the 1700s, when Jesus is said to have appeared to a young shepherd in the form of another boy. (Photo by Rodrigo Abd/AP Photo)

Damselflies covered in dew rest on a wild flower by the Po River, northern Italy on August 15, 2016. (Photo by Alberto Ghizzi Panizza/Barcroft Images)

A dog takes a dip in the river Elbe on February 6, 2012 in Hamburg, Germany.The current cold front that has claimed over 200 lives in eastern Europe makes its way west. (Photo by Stuart Franklin/Getty Images)