“Hippo Chase”. As we approached the camp the Selinda Reserve of northern Botswana our boat passed by a hippo resting in the water. I turned around to look back at the boat's wake and saw the hippo charging after us! The hippo must've been tired from an all-nighter because he was angry. He rose way up out of the water three times trying to chase our boat! He was coming at us with such force that he created a wake of his own. Photo location: Selinda Reserve of northern Botswana. (Photo and caption by Curtis Simmons/National Geographic Photo Contest)

Spectators cheer as the United Launch Alliance Delta 4-Heavy rocket, with NASA's Orion spacecraft mounted atop, lifts off from the Air Force Station, December 5, 2014, in Cape Canaveral, Fla. (Photo by Smiley N. Pool/AP Photo/Houston Chronicle)

A boy takes a picture of a car crash in Shenzhen, Guangdong province, August 4, 2014. Two passengers were sent to hospital but no death was reported as a result of the accident, according to local media. (Photo by Reuters/Stringer)

A one month old Turquoise colored Green Veiled Chameleon perches on a finger in the Cardin's Chameleons boothat Repticon 2014 Sunday, August 3, 2014 in Jacksonville, Fla. The vendor specializes in captive bred and born Veiled Chameleons and this particular specimen cost $40.00. The Repticon reptile and Exotic Animal show made its stop in Jacksonville over Saturday and Sunday offering a variety of cold blooded critters and related supplies for sale at the University Center on the University of North Florida campus. The show, which travels nationally stops in Jacksonville several times a year according to event vendor team leader Patty Healey. (Photo by Bob Self/AP Photo/The Florida Times-Union)

Visitors run away as waves caused by a tidal bore surge past a barrier on the banks of Qiantang River, in Hangzhou, Zhejiang province August 13, 2014. (Photo by Reuters/Stringer)

A model presents a creation from the Jeremy Scott Spring/Summer 2015 collection during New York Fashion Week September 10, 2014. (Photo by Lucas Jackson/Reuters)

NASA's DHC-3 Otter plane flies in Operation IceBridge-Alaska surveys of mountain glaciers in Alaska in this image released on September 18, 2014. Over the past few decades, average global temperatures have been on the rise, and this warming is happening two to three times faster in the Arctic. (Photo by Chris Larsen/Reuters/NASA/University of Alaska-Fairbanks)

A woman takes a photograph of a sculpture titled “Couple Under an Umbrella, 2013” by Australian sculptor Ron Mueck during a preview of his exhibition at the Pinacoteca Museum in Sao Paulo November 19, 2014. (Photo by Nacho Doce/Reuters)