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.)

Željava Air Base, situated on the border between Croatia and Bosnia and Herzegovina under Plješevica Mountain, near the city of Bihać, Bosnia, was the largest underground airport and military air base in the former Yugoslavia, and one of the largest in Europe. (Photo by Thomas Windisch/Exclusivepix Media)

From stuffed elephants to picnics under power lines, Leipzig-born photographer Frank Herfort coaxes magical, colour-saturated tableaux from intriguing slices of everyday Russian life. Here: A lonely dog watches the mailboxes in a typical Moscow residential block. (Photo by by Frank Herfort/The Guardian)

A little girl holding her newborn sister waits for their turn in a queue during a vaccination campaign under the supervision of the Syrian Arab Red Crescent (SARC) humanitarian nonprofit organization, in the besieged Syrian town of Douma, Syria, 23 May 2017. According to a statement from SARC, in the city of Douma some 12,809 children under the age of five were immunized in a vaccination campaign to prevent measles and poliomyelitis. The campaign was the first of its kind with the participation of 100 volunteers. SARC has been delivering vaccines to 17 health centers approved for vaccination campaigns in towns and villages in the Eastern Ghouta area. (Photo by Mohammed Badra/EPA)

Indonesian mahouts clean their Sumatran elephant in a river near the zoo in Medan, North Sumatra, Indonesia, 12 December 2014. According media reports, the smallest of the Asian elephants, Sumatran elephant (Elephas maximus sumatrensis) is facing serious pressures arising from illegal logging and associated habitat loss and fragmentation in Indonesia. The population has come under increasing threat from rapid forest conversion to plantations. (Photo by Dedi Sahputra/EPA)

Rescuers search for survivors in the rubble of a collapsed residential building in Makongeni estate in Nairobi December 17, 2014. Three more bodies were recovered on Wednesday night from the building that collapsed in Makongeni estate in Nairobi, raising the death toll to four, Kenya Red Cross has reported. The residential building whose sixth floor was still under construction had allegedly not been cleared for occupation by the Nairobi City County and its owner has been missing since it collapsed. A search and rescue and rescue operation is ongoing for the unknown number of people still trapped under the rubble, Kenya Red Cross also reported. (Photo by Thomas Mukoya/Reuters)

In this April 2, 2015 photo, dog owner Laura Aquilina strolls with her two year old Rottweiler Brutus, who was recently fitted with prosthetics on all four paws, and is currently learning to use them, near Aquilina's home in Loveland, Colo. Brutus lost all four paws to frostbite as a puppy while under care of a breeder, and Aquilina began caring for him about a year ago. (Photo by Brennan Linsley/AP Photo)