Runner-up; Hon Yen marine ecosystem. Phu Yen, Vietnam. Every year between May and August, the coral of this rich and diverse ecosystem becomes exposed at low tide. (Photo by Truong Hoai Vu/Royal Society of Biology Photography Competition)

Mud Madness at the annual Jaffa Cakes charity three-mile run at Foymore Lodge near Portadown this afternoon, on April 13, 2014. A total of a thousand competitors and fun-runners took part in the two races held over the mudstrewn endurance course. (Photo by Alan Lewis/Photopress Belfast)

Runners rest inside Kim Il Sung Stadium in Pyongyang, North Korea on Sunday, April 14, 2013. North Korea hosted the 26th Mangyongdae Prize Marathon to mark the upcoming April 15, 2013 birthday of the late leader Kim Il Sung. (Photo by Alexander F. Yuan/AP Photo)

A man takes pictures at the finish line during the Colour Run at Centennial Park in Sydney August 25, 2013. According to organizers, 15,000 runners registered to complete the 5km (3 miles) course in Centennial Park on Sunday, being covered in blue, pink, orange and yellow powder on their way to the finish line. (Photo by Daniel Munoz/Reuters)

Some two thousand runners dressed as Santa Claus make their way through Clapham Common during The London Santa Dash, to raise money for Great Ormond Street Hospital, in London, Britain December 4, 2016. (Photo by Dylan Martinez/Reuters)

Indian Runner ducks march past farm buildings at the Vergenoegd wine estate near Cape Town, South Africa, May 16, 2016. Each day, a quack squad of killer ducks are released for the first of two sorties at South Africa's Vergenoegd wine farm in Stellenbosch. Their mission – seek and destroy thousands of pests out to ruin the season's harvest. Fanning out across the vineyards, some 1,000 Indian Runner ducks hone in on their hidden targets with uncanny precision, locating the tiny white dune snails feasting on budding vines. (Photo by Mike Hutchings/Reuters)

A devotee offers oil lamps on top of his body as part of a ritual during Dashain, the biggest religious festival for Hindus in Bhaktapur, Nepal, October 22, 2015. Hindus in Nepal celebrate victory over evil during the festival by flying kites, feasting, playing swings, sacrificing animals and worshipping the Goddess Durga as well as other gods and goddess as part of celebrations held throughout the country. (Photo by Navesh Chitrakar/Reuters)

A runner tries to get the attention of a bull, named Santon, during the “Toro de Cuerda” (Bull on Rope) festival at Plaza de Espana square in Grazalema, southern Spain, July 18, 2016. Three bulls restrained by a rope are allowed to run through the streets of the village during the annual festival. (Photo by Jon Nazca/Reuters)