In this March 14, 2015 photo, tourists take pictures from a viewing area at Iguazu Falls in Brazil. From walkways and bridges, viewers can count 270 water falls almost 100 meters (330 feet) high. (Photo by Jorge Saenz/AP Photo)

Residents cross a swelling dam, due to rising waters brought about by Typhoon Koppu, in Las Pinas city, metro Manila October 19, 2015. Powerful typhoon Koppu ploughed into the northeastern Philippines before dawn on Sunday destroying homes and displacing 10,000 people and whipping up coastal surges four meters (12 feet) high, disaster agency officials said. (Photo by Ezra Acayan/Reuters)

A demonstrator dressed as Santa Claus holds up a flag as a riot police vehicle releases a jet of water during a protest against the private system of pension fund administrators in Santiago, Chile, December 10, 2015. The flag reads “Classist Workers Union”. (Photo by Ivan Alvarado/Reuters)

A tractor trailer drives through flash flood waters that overran Skunk Creek, Tuesday, August 19, 2014, in northwestern Phoenix. Flooding from heavy rain in the Phoenix area has forced authorities to close several major roads, including a portion of Interstate 17 about 25 miles north of the city. (Photo by Matt York/AP Photo)

A mother bear takes a dip in the water to cool off in the warm summer sun but refuses to leave her three youngsters behind – so they climb aboard her back. (Photo by Jon Langeland/Solent News & Photo Agency)

David Hall’s photographs of scenery and creatures off the coast of Canada in the Pacific Northwest portray serenity under the water, which belie the extreme challenges he faces to get his images. For each shoot, Hall wears a dry suit, a neoprene body suit that covers all of his body but his head and traps air inside to keep him warm. Water temperature in Canada’s British Columbia typically ranges between 45 and 50 degrees Fahrenheit. Photo: Moon jellyfish and cross jellies. (Photo by David Hall)

An anti-government protester wearing a Guy Fawkes mask stands with a shield near flames from molotov cocktails thrown at a water cannon by anti-government protesters during riots in Caracas in this April 20, 2014 file photo. (Photo by Jorge Silva/Reuters)

A heat-stressed koala waits as a resident pours water on its back on December 19, 2015 in Adelaide, Australia. Adelaide is experiencing an extreme heatwave, with temperatures reaching over 40 degrees for five consecutive days. (Photo by Morne de Klerk/Getty Images)