Recruits who earned a place in the Motivation Platoon struggle through water and muck on their way to becoming a Marine or going into some other line of work, October 7, 1971. (Photo by Eddie Adams/AP Photo)

Soldiers of People's Liberation Army (PLA) Lanzhou Military Region jump through a burning obstacle during a training session at a military base in Tianshui, Gansu province, China, January 6, 2016. (Photo by Reuters/Stringer)

Costumed guests arrive for the “Life Ball” charity event at the Rathaus city hall in Vienna, Austria, 10 June 2017. The 24th Life Ball is a charity fundraiser for HIV and Aids projects. (Photo by Christian Bruna/EPA/EFE)

Convicted murderer Hector Alvarado Mazariegos, right, drops to the ground as he is hit by bullets of a Guatemala firing squad in the public cemetery at Mazatenango, June 28, 1975. His companion, Rocael Ortiz, met the same fate a few seconds later. Both were convicted of murder. (Photo by AP Photo/Anzueto)

A young woman takes pictures of the city with her mobile phone, from the glass-floor observation platform, in the Oriental Pearl Tower, in the financial district of Shanghai, on May 9, 2019. (Photo by Hector Retamal/AFP Photo)

Union Berlin players celebrate after the Bundesliga playoff second leg match between 1. FC Union Berlin and VfB Stuttgart at Stadion an der alten Foersterei on May 27, 2019 in Berlin, Germany. (Photo by Annegret Hilse/Reuters)

A boy plays on the glass at Thailand's first skywalk in Bangkok, Thailand on November 18, 2018. (Photo by Soe Zeya Tun/Reuters)

Girls dressed in traditional costumes run as men throw water on them as part of Easter celebrations during a presentation to the media in Mezokovesd, Hungary, April 13, 2017. (Photo by Laszlo Balogh/Reuters)