A man from Dinka tribe holds his AK-47 rifle in front of cows in a Dinka cattle herders camp near Rumbek, capital of the Lakes State in central South Sudan December 14, 2013. (Photo by Goran Tomasevic/Reuters)

A tourist jumps inside an upside-down house at Fengjing Ancient Town, Jinshan District, south of Shanghai, May 1, 2014. The upside-down house was built as a tourist attraction using everyday household items and furniture. (Photo by Aly Song/Reuters)

A man pours mud water on the head of his girl friend during the Boryeong Mud Festival at Daecheon Beach in Boryeong, South Korea, Friday, July 18, 2014. The annual mud festival features mud wrestling and mud sliding. (Photo by Ahn Young-joon/AP Photo)

Large waves break at Burleigh Heads on the Gold Coast,, Queensland, Australia, 05 June 2016. Recent wild weather unleashed heavy rainfalls, powerful winds and abnormally high tides in Southeast Queensland and northern New South Wales. (Photo by Dan Peled/EPA)

2016 Rio Olympics, Swimming, Preliminary, Men's 100m Backstroke, Heats, Olympic Aquatics Stadium, Rio de Janeiro, Brazil on August 7 2016. Christopher Reid (RSA) of South Africa competes. (Photo by Dominic Ebenbichler/Reuters)

People participate in a wet t-shirt contest on a stage while people party and celebrate on the beach at Clayton's Beach Bar and Grill in South Padre Island, Texas, USA, 11 March 2018. Spring break draws thousands of kids from all over the country to many different locations to celebrate each year. (Photo by Larry W. Smith/EPA/EFE)

Riders negotiate a dune as they compete in the Adult Solo race at the HydroGarden Weston Beach Race in Weston- super- Mare, south west England, on October 9, 2016. Beach racing is an offshoot of enduro and motocross racing. Riders on solo motorcycles and quad bikes compete on a course marked out on a beach, with man- made jumps and sand dunes being constructed to make the course tougher. (Photo by Adrian Dennis/AFP Photo)

Iraqi Shiite fighters from the Hashed al- Shaabi (Popular Mobilisation) paramilitaries hold a position near the village of Tal Abtah, south of Tal Afar, on November 30, 2016, during a broad offencive by Iraq forces to retake the city Mosul from Islamic State group jihadists. (Photo by Ahmad Al- Rubaye/AFP Photo)