A reveller takes part in the battle of “Enfarinats”, a flour fight in celebration of the Els Enfarinats festival on December 28, 2015 in Ibi, Spain. Citizens of Ibi annually celebrate the festival with a battle using flour, eggs and firecrackers. (Photo by Pablo Blazquez Dominguez/Getty Images)

Riot police stand guard behind a fire as refinery workers hold a blockade of the oil depot of Douchy-Les-Mines to protest against the government's proposed labour reforms, on May 25, 2016. Refinery workers stepped up strikes that threaten to paralyse France weeks ahead of the Euro 2016 tournament as the government moved to break their blockades, escalating a three-month tug-of-war over labour reforms. (Photo by François L.O./AFP Photo)

Lilly Caron, 8, of Bridgeton, Maine, Jason Homchick, of San Diego, and Lilly's father Jason Caron, (obscured), ride the Sky Swing at Seacoast Adventure, Thursday, July 14, 2016, in Wyndham, Maine. The 100-foot-tall swing gives riders the combined thrills of sky diving and hang gliding. (Photo by Robert F. Bukaty/AP Photo)

This photo taken on August 7, 2016 shows mahjong enthusiasts playing mahjong under water in a swimming pool at a diving club in the Chinese city of Chongqing. Only participants with proper diving certification were allowed to take part in the underwater competition. (Photo by AFP Photo/Stringer)

Riot police walk in the street as a couple kiss on June 15, 2011 in Vancouver, Canada. Vancouver broke out in riots after their hockey team the Vancouver Canucks lost in Game Seven of the Stanley Cup Finals. (Photo by Rich Lam/Getty Images)

The land-robot “teleMAX” of German company telerob stands next to soldiers during a trial at the German army base on May 18, 2010 in Hammelburg, Germany. ELROB provides an overview of the current state of affairs in European unmanned system technology and to evaluate commercial off-the-shelf products for military use. It is to show what is feasible in robotics, to support technological developments in Europe, and to find solutions for the current military challenges. (Photo by Ralph Orlowski/Getty Images)

A Burmese worker sets up Christmas lights inside a woman's clothing store inside a shopping mall December 6, 2011 in Nay Pyi Taw, Myanmar. (Photo by Paula Bronstein/Getty Images)

An elephant “kisses” a visitor during a show at an elephant training school in Xishuangbanna, Yunnan province, April 18, 2015. Some 16 elephants live at the school and give four 30-minute performances everyday for visitors. (Photo by Wong Campion/Reuters)