In this May 8, 2015 photo, sisters Zoraida Infante, left, and Graciela Trujillo pray on Fishermen's Beach before therapeutic swimming in the Pacific Ocean in Lima, Peru. Under overcast skies, the bathers practice thalassotherapy, which derives from the Greek “thalasso”, for “sea”, and draws on the ocean's healing properties. (Photo by Rodrigo Abd/AP Photo)

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)

A woman stands next to a giant jandal on Tamarama Beach as giant sculptures are installed ahead of the “Sculpture by the Sea” exhibition in Sydney on October 19, 2016. Celebrating it's 20th anniversary, Sculpture by the Sea is the world's largest annual, free-to-the-public, outdoor sculpture exhibition. (Photo by William West/AFP Photo)

Tracy Sarita celebrates the sunrise during the Burning Man 2015 “Carnival of Mirrors” arts and music festival in the Black Rock Desert of Nevada, September 3, 2015. Approximately 70,000 people from all over the world are gathering at the sold-out festival to spend a week in the remote desert to experience art, music and the unique community that develops. (Photo by Jim Urquhart/Reuters)

Astrid Perez (L) and Ramon Camacho lay on the Playa during the Burning Man 2015 “Carnival of Mirrors” arts and music festival in the Black Rock Desert of Nevada, September 6, 2015. Sunday marks the last day of the sold-out festival that gathered approximately 70,000 people from all over the world. (Photo by Jim Urquhart/Reuters)

A climber walks on the ridge beneath the eastern peak of the Gamsberg (2385 meters above sea level) near Grabs, Switzerland, Friday, October 3, 2014. (Photo by Gian Ehrenzeller/AP Photo/Keystone)

Mikhail Kalashnikov, the father of the world's most popular assault rifle, is handed an AK-74 November 23, 2002 in Izhevsk,1000 East km. from Moscow. November 23 marked the 55th anniversary of the release of the first Kalashnikov gun. According to the Moscow-based Center for Analysis of Strategic and Technologies some 70 million to 100 million Kalashnikovs have been built worldwide since 1947, compared about 7 million to Kalashnikov's Western rival the M-16 assault rifles. (Photo by Oleg Nikishin/Getty Images)