The NASA Extreme Environment Mission Operations (NEEMO) 21 mission began on July 21 as an international crew of aquanauts splashed down to the undersea Aquarius Reef Base, located 62 feet below the surface of the Atlantic Ocean in the Florida Keys National Marine Sanctuary. The NEEMO 21 crew will perform research both inside and outside the habitat during a 16-day simulated space mission. During simulated spacewalks carried out underwater, they will evaluate tools and mission operation techniques that could be used in future space missions, including journeys to Mars. (Photo by Karl Shreeves/NASA)

Two young boys kneel on stools on either side of a round table as one uses a match to this the other's cigarette, November 12, 1928. (Photo by FPG/Getty Images)

Supporters of U.S. Democratic presidential nominee Hillary Clinton react at her election night rally in Manhattan, New York, U.S., November 8, 2016. (Photo by Lucas Jackson/Reuters)

Protesters on a freeway onramp amid a chaotic traffic situation with the shutdown of the freeway in downtown Los Angeles, California after midnight early on November 10, 2016 as protesters angry over Donald J. Trump's election as the next US president marched in downtown Los Angeles through the evening and shut down portions of the Hollywood (101) Freeway. Thousands of protesters rallied across the United States expressing shock and anger over Donald Trump's election, vowing to oppose divisive views they say helped the Republican billionaire win the presidency. (Photo by Frederic J. Brown/AFP Photo)

Vietnamese female commissioned officers of the signal force march during a parade marking their 70th National Day at Ba Dinh square in Hanoi, Vietnam September 2, 2015. (Photo by Reuters/Kham)

In this April 4, 2014 file photo, a community policeman kicks a man who they alledge participated in an ambush against them near the town of La Concepcion, Mexico. The vigilante force was set-up by affected communities opposed to the construction of the La Parota hydroelectric dam. Two vigilantes were injured and one died. (Photo by Bernandino Hernandez/AP Photo)

A model falls and gets help back to her feet during the fashion show for the Givenchy Spring 2016 collection at Fashion Week on, Friday, September 11, 2015, in New York. (Photo by Bebeto Matthews/AP Photo)

Russia's synchronised swimming duet Aleksandr Maltsev (L) and Darina Valitova compete in the Mixed Duet Technical preliminary during the synchronised swimming competition at the 2015 FINA World Championships in Kazan on July 25, 2015. (Photo by Christophe Simon/AFP Photo)