Armed Karo herdsman just back from protecting their cattle herds come down to the river to wash decorative clay markings off their bodies at the end of the day in the Omo Valley, South West Ethiopia. Dus, Omo Valley, Ethiopia, January 2008. (Photo by Brent Stirton/Discovery Communications)

A devotee carrying an idol of the Hindu god Ganesh, the deity of prosperity, jumps into the Sabarmati river to immerse the idol on the last day of the 10-day-long Ganesh Chaturthi festival in Ahmedabad, India, September 27, 2015. (Photo by Amit Dave/Reuters)

Olaf Niess catches swans on the river Alster near the town hall in Hamburg, Germany, 17 November 2015. The Alster swans are moving to their ice-free winter quarters on the Eppendorf Muehlenteich millpond until spring. (Photo by Bodo Marks/EPA)

Revellers cool themselves in the Danube River during the Sziget music festival on an island in Budapest, Hungary August 12, 2015. The event is one of the biggest cultural events of Europe, offering art exhibitions, theatrical and circus performances and music concerts. Almost 200 performers from 47 countries will entertain the hundreds of thousands of visitors from 11 to 18 August. (Photo by Laszlo Balogh/Reuters)

Naga Sadhus or Hindu holy men, smeared with ash, drink tea inside their makeshift camps near the confluence of river Ganges and the Bay of Bengal, ahead of Makar Sankranti festival at Sagar Island, south of Kolkata January 13, 2015. Hindu monks and pilgrims are making their annual trip to Sagar Island for the one-day festival of “Makar Sankranti” on Wednesday. (Photo by Rupak De Chowdhuri/Reuters)

Snow covers roofs, streets and the Charles River following a winter blizzard in Boston, Massachusetts January 28, 2015. A powerful blizzard struck Boston and surrounding New England on Tuesday, leaving some 4.5 million people grappling with as much as three feet of snow and coastal flooding. (Photo by Brian Snyder/Reuters)

A 5.5 metre massive crocodile makes mince meat out of a bull shark in Kakadu's Adelaide River on August 5, 2014 in Kakadu, Australia. The crocodile forced the bull shark into the mangroves and devoured the bull shark. A 43 year old Sydney father took these exclusive photos in the Northern Territory. (Photo by Andrew Paice/Getty Images)

The giant inflatable Rubber Duck installation by Dutch artist Florentijn Hofman floats on the Parramatta River, as part of the 2014 Sydney Festival, in Western Sydney, January 10, 2014. The creation is five stories tall and five stories wide and has been seen floating in various cities around the world since 2007. (Photo by Jason Reed/Reuters)