Participants climb over a wall at the “Tough Mudder” endurance event series in Arnsberg September 6, 2014. Competitors who took part in the endurance event saw themselves having to overcome various military style obstacles. (Photo by Ina Fassbender/Reuters)

Sgt. William Olas Bee, a U.S. Marine from the 24th Marine Expeditionary Unit, has a close call after Taliban fighters opened fire near Garmsir in Helmand Province of Afghanistan, May 18, 2008. (Photo by Goran Tomasevic/Reuters)

A member of the “Exit Point” amateur rope-jumping group jumps from a 44-metre high (144-feet high) waterpipe bridge in the Siberian Taiga area outside Krasnoyarsk, September 28, 2014. Fans of rope-jumping, a kind of extreme sport involving a jump from a high point using an advanced system of amortization including mountaineering and rope safety equipment, attended the Golden Autumn group's jumping season. (Photo by Ilya Naymushin/Reuters)

“A Mothers Tail”. A baby cub pulls on his mother's tail to get attention. Photo location: Masai Mara, Kenya. (Photo and caption by Tori Marsh/National Geographic Photo Contest)

Juno, a Beluga whale, greets a young viewer at the Mystic aquarium in Connecticut, USA on December 5, 2015. (Photo by Tim Clayton/Corbis)

Ally Brooke, from left, Dinah-Jane Hansen, Camila Cabello, Lauren Jauregui and Normani Hamilton of Fifth Harmony, perform “Work From Home” at the Billboard Music Awards at the T-Mobile Arena on Sunday, May 22, 2016, in Las Vegas. (Photo by Chris Pizzello/Invision/AP Photo)

An Indian girl smiles under a water splash at a water park as the temperatures reached 38 degree Celsius in Calcutta, eastern India, 12 June 2016. The summer or pre-monsoon season lasts from March to July in eastern India with the highest day temperatures ranging from 38 to 45 degrees Celsius. (Photo by Piyal Adhikary/EPA)

Hundreds of people pack the Canaveral national seashore's Playalinda Beach as a United Launch Alliance Atlas V rocket, carrying a U.S. Navy communications satellite, lifts off from Complex 41 at the Cape Canaveral Air Force Station, Friday, June 24, 2016, in Cape Canaveral, Fla. The satellite is designed to significantly improve ground communications for U.S. forces on the move. (Photo by Craig Rubadoux/Florida Today via AP Photo)