A competitor scrambles in the mud under barbed wire during the Tough Guy Challenge 2009 at South Perton Farm on February 1, 2009 in Wolverhampton, England. The biannual event to raise cash for charity challenges thousands of international competitors to run through a gruelling set of 21 obstacles including water, fire and tunnels after a lengthy run at the start. (Photo by Christopher Furlong/Getty Images)

Without the use of any type of scuba equipment, divers descend to great depths armed with underwater guns, harpoons and strong line to stalk and hunt prey. Some of the best free-divers in the world can hold their breath for up to 5 minutes under water and go to depths greater than 100 feet.

(All photography © Eyeconic Images.)

An injured vulture is treated at the VulPro Vulture Rehabilitation Centre in Hartebeepoortdam in the Magalisburg region on September 15, 2015. Confined to southern Africa, just under 4,000 breeding pairs of Cape Vultures remain in the wild, mostly in South Africa, Lesotho and Botswana. Unless conservation efforts are successful, Africa's largest vulture species may be facing eventual extinction. (Photo by Mujahid Safodien/AFP Photo)

A girl cover her face while riding a motorcycle as haze shrouds a street near Tanjung Siapi Api port in Palembang, on the Indonesian island of Sumatra, September 19, 2015. Indonesia will take 30 days to bring smouldering forest fires under control, the national disaster management agency said on Friday, as smog from the fires pushes pollution in Southeast Asia to record highs. (Photo by Reuters/Beawiharta)

A 13-month-old chimp named Fumo carries a “Christmas present” of food treats in wrapping paper under his arm during a Christmas-themed feeding time at Sydney's Taronga Park Zoo, December 9, 2014. Fumo, meaning “chief” or “spear” in Swahili, is one of the latest additions to the zoo's successful primate breeding program. (Photo by Jason Reed/Reuters)

An approximately 8 year-old male orangutan named Siamang reacts under the influence of tranquilizer as it's being prepared to be released into the wild at a rehabilitation center in Kuta Mbelin, North Sumatra, Indonesia, Friday, July 10, 2015. The orangutans at the center were mostly rescued from palm oil plantations or confiscated from homes where they were kept as pet animals. Orangutan populations in Indonesia's Borneo and Sumatra island are facing severe threats from habitat loss, illegal logging, fires and poaching. Conservationists predicted that without immediate action, orangutans are likely to be the first great ape to become extinct in the wild. (Photo by Binsar Bakkara/AP Photo)

Palestinians hit injured Israeli settlers, center, detained by Palestinian villagers in a building under construction near the West Bank village of Qusra, southeast of the city of Nablus, Tuesday, January 7, 2014. Palestinians held more than a dozen Israeli settlers for about two hours Tuesday in retaliation for the latest in a string of settler attacks on villages in the area, witnesses said. The military said the chain of events apparently began after Israeli authorities removed an illegally built structure in Esh Kodesh, a rogue Israeli settlement in the area. In recent years, militant settlers have often responded to any attempts by the Israeli military to remove parts of dozens of rogue settlements, or outposts, by attacking Palestinians and their property. The tactic, begun in 2008, is known as “price tag”. (Photo by Nasser Ishtayeh/AP Photo)