A stray puppy walks along abandoned train tracks near the Chernobyl nuclear power plant on August 19, 2017 near Chornobyl, Ukraine. An estimated 900 stray dogs live in the exclusion zone, many of them likely the descendants of dogs left behind following the mass evacuation of residents in the aftermath of the 1986 nuclear disaster at Chernobyl. (Photo by Sean Gallup/Getty Images)

A group of people are seen on a Victoria line train in London, England during the first night of the Night Tube service on August 19 2016. The Central line and Victoria line are the first to operate a Night service with further lines expected to be running by the end of the year. (Photo by SWNS.com)

Jun Sato (2nd L), founder of Japan's first parkour educational institute SENDAI X-TRAIN, demonstrates his parkour skill with other practitionners at a park in Tokyo, Japan November 2, 2016. (Photo by Kim Kyung-Hoon/Reuters)

Street photographer Yassine Alaoui Ismaili follows 16-year-old Emeer Guesmi, aka B-boy Zulu Rema, as he trains and performs breakdance moves – all without the use of his legs. At a breakdance championship in Tunisia, Casablanca-based street photographer Yassine Alaoui Ismaili noticed an unusual competitor: Emeer Guesmi, dancing without the aid of his lower legs. He started following him as he trained and performed. (Photo by Yassine Alaoui Ismaili/The Guardian)

The series of shots show the bare steel infrastructure of the Bushfield army training camp near Winchester which was in operation during World War Two and was used to train Royal Green Jackets recruits in the sixties. The spectacular images were taken by an urban explorer who wished to remain anonymous. Here: A railway siding in Wiltshire, UK where ammunition was transferred by tunnel to an underground storage facility. (Photo by MediaDrumWorld.com)

Students of the General Yermolov Cadet School take part in combined military training with members of a local youth military patriotic club at a boot camp of the Russkiye Vityazi (Russian Knights) military patriotic club in the village of Sengileyevskoye outside Stavropol, Russia February 8, 2017. (Photo by Eduard Korniyenko/Reuters)

Israeli soldiers from the mixed-gender Lions of the Jordan battalion, under the Kfir Brigade, check their weapons at the end of the last training before being assigned their posting, on February 28, 2017, near the West Bank village of Bardale, east of Jenin. (Photo by Jack Guez/AFP Photo)

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)