A competitor shouts as he takes part in the “Tough Guy” adventure race near Wolverhampton, central England, on January 29, 2017. The Tough Guy event, which is being held for the final time in its 30th year, challenges thousands of competitors to run a gruelling course whilst negotiating over 200 obstacles including: water, fire, and tunnels. (Photo by Oli Scarff/AFP Photo)

Popular Mobilization Forces (PMF) fires towards Islamic State militants during a battle with Islamic State militants, west of Mosul, Iraq February 22, 2017. (Photo by Reuters/Stringer)

People dressed as zombies take part in a “Zombie Walk” parade in Athens, Greece, February 25, 2017. (Photo by Michalis Karagiannis/Reuters)

A picture taken on March 16, 2017 shows women dressed up as mermaids posing by a pool at a mermaid training school in Moscow. Russian women who have dreamt of becoming a mermaid since their youngest years, start turning their fantasies into reality with a new type of fitness – mermaid swimming. (Photo by Natalia Kolesnikova/AFP Photo)

Mermaid Hales Parcells geets children as she performs at the Virginia Aquarium in Virginia Beach, Va., Monday, April 3, 2017. The Aquarium presents a mermaid show one night each week during the month of April. (Photo by Steve Helber/AP Photo)

Nuns react at the arrival of Pope Francis at the St. Mary's school to attend a meeting of clergy and religious in Nairobi, Kenya, 26 November 2015. Pope Francis is on a six days visit that will take him to Kenya, Uganda and the Repulic of Central Africa from 25 to 30 November. (Photo by Daniel Dal Zennaro/EPA)

Children walk past the partially collapsed boundary wall of a school and a Buddhist shrine that were damaged during the earthquake earlier this year at Khumjung, a typical Sherpa village in Solukhumbu district also known as the Everest region, in this picture taken November 30, 2015. (Photo by Navesh Chitrakar/Reuters)

Italian Air Force's aerobatic demonstration team, the Frecce Tricolori leave colourful vapour trails as they fly over the Altare della Patria monument on Republic Day (Festa della Repubblica) in Rome, Italy, 02 Jun 2017. The anniversary marks the founding of the Italian Republic in 1946. (Photo by Massimo Percossi/EPA)