A female Marine prepares to throw a practice grenade during Marine Combat Training (MCT) on February 21, 2013 at Camp Lejeune, North Carolina. Since 1988 all non-infantry enlisted male Marines have been required to complete 29 days of basic combat skills training at MCT after graduating from boot camp. MCT has been required for all enlisted female Marines since 1997. About six percent of enlisted Marines are female. (Photo by Scott Olson)

An animatronic dragon performs during the launch of How To Train Your Dragon Arena Spectacular at a Dreamworks and Global Creatures media call on August 8, 2011 in Melbourne, Australia. (Photo by Quinn Rooney/Getty Images)

A performer poses with “The Gronkle” and “Deadly Nadder” at the How to Train Your Dragon Media Call at Fox Studios on November 29, 2011 in Sydney, Australia. The “How to Train Your Dragon Arena Spectacular” world premiere will take place in Australia in March 2012. (Photo by Brendon Thorne/Getty Images)

A general view of atmosphere during the NYC “Soul Train” Line Flash Mob: Hippest Trip in America in honor of Don Cornelius in Times Square on February 4, 2012 in New York City. Cornelius, the creator of “Soul Train”, died on February 1, 2012 at the age of 75. (Photo by Ilya S. Savenok/Getty Images)

Children watch their classmate pour cold water on herself under the watch of a fitness coach at a local kindergarten in Russia's Siberian city of Krasnoyarsk, March 11, 2015. The program, which also involves sports training and sauna usage, has been practiced by the kindergarten for more than 15 years as they believe it has health benefits and keeps the children fit. Children start pouring cold water on themselves outdoors after about three years of training and undergoing medical tests, and the kindergarten is the only one in the region that practices these exercises, according to employees. (Photo by Ilya Naymushin/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)

In this Friday, February 27, 2015 photo, an Israeli high-school senior preparing to join the Israeli military later this year participates in a privately run training camp for military combat fitness near Yakum, central Israel. With a mandatory three-year military service looming after graduation, teenage boys, and increasingly girls too, are gearing up for the draft, getting into shape and trying to improve their chances of acceptance into elite combat units. (Photo by Oded Balilty/AP Photo)