A visitor feeds a food pellet to a giraffe in the Giraffe Centre in Nairobi, Kenya January 15, 2017. (Photo by Goran Tomasevic/Reuters)

St Andrews University students skinny dip in the sea as May Day celebrations in St Andrews, Scotland on April 30, 2017. Hundreds of revellers ditched their clothes and bravely jumped into the bitterly cold North Sea. (Photo by Alamy Stock Photos)

The car driven by Scott Dixon, of New Zealand, goes over the top of Jay Howard, of England, in the first turn during the running of the Indianapolis 500 auto race at Indianapolis Motor Speedway, Sunday, May 28, 2017, in Indianapolis. (Photo by Marty Seppala/AP Photo)

A person jumps on a trampoline before Nathan's Famous Fourth of July International Hot Dog-Eating Contest at Coney Island in Brooklyn, New York City, U.S., July 4, 2017. (Photo by Andrew Kelly/Reuters)

Two female revelers engage in a beer drinking contest in the Hacker Pschorr tent on the first day of the 2017 Oktoberfest beer fest on September 16, 2017 in Munich, Germany. Oktoberfest is the world's largest beer celebration and typically draws over six million visitors over its three-week run. Oktoberfest includes massive beer tents, each run by a different Bavarian brewer, as well as amusement rides and activities. (Photo by Philipp Guelland/Getty Images)

Mount Agung's eruption is seen next to a Balinese temple at Kubu sub-district in Karangasem Regency on Indonesia's resort island of Bali on November 26, 2017. Indonesia authorities raised the alert for the rumbling volcano to highest level on Monday and closed the international airport on tourist island of Bali stranding thousands of travelers. (Photo by Sonny Tumbelaka/AFP Photo)

A Los Angeles County Fire helicopter flies over during the “Skirball Fire” which began early morning in Bel-Air, California, USA, 06 December 2017. An outbreak of several fires North of Los Angeles has occurred as one of the strongest Santa Ana winds forecast of the season is ongoing and expected to last several days. (Photo by John Cetrino/EPA/EFE)

A US Marine leads two Viet Cong suspects in restraints during the Tet Offensive on February 20, 1967. (Photo by Bettmann Archive/Getty Images)