“David Doubilet (born 28 November 1946) is a well known underwater photographer known primarily for his work published in National Geographic Magazine. He was born in New York and started taking photos underwater at the young age of 12. He started with a Brownie Hawkeye in a rubber anesthesiologist's bag to keep the water out of the camera. During his summer holidays, he spent his time along the New Jersey coast. He later worked as a diver and photographer for the Sandy Hook Marine Laboratories in New Jersey. He also spent much time in the Caribbean. While a dive instructor in the Bahamas he found his motivation to capture the beauty of the sea and everything in it”. – Wikipedia. (Photo by David Doubilet/National Geographic)

A visitor walks past the life-size sculpture “Security Guard” by Marc Sijan at The Armory Show, New York's annual international art fair, at Piers 92 and 94 on March 9, 2012 in New York City. The show features paintings, photographs, sculpture and other works of art by artists including Andy Warhol, Cindy Sherman and Pablo Picasso. (Photo by Mario Tama/Getty Images)

California-based photographer Seth Casteel made his name taking photographs of dogs underwater, but before that, he was snapping cats on land.

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.)

Project Mermaids model. Project Mermaids lets ocean-lovers don tails and live out their siren fantasies. Clients can pay for a shoot that is either on land or underwater, with the images looking to raise awareness about preservation of beaches, seas and oceans. The project – which is shot by photographers Angelina Venturella and Chiara Salomoni – started purely to raise awareness, with celebrities dressing up as sirens as part of the cause. (Photo by Angelina Venturella/Chiara Salomoni/Caters News Agency)

A giant sculpture of a seven-month-old baby by artist Marc Quinn entitled “Planet” contrasts against the stately grandeur of Chatsworth House and the Derbyshire countryside on 4 September, 2008, Chatsworth, England. The bronze sculpture painted white is part of the Beyond Limits exhibition of modern and contemporary sculpture displayed in the gardens of Chatsworth by Sotherby's. More than 20 works will be on display from 9 September to 2 November 2008. In past years acclaimed artists Damien Hirst, Antony Gormley, Salvador Dali and Henry Moore have had work exhibited. (Photo by Christopher Furlong/Getty Images)

These photographs appear to show a spectacular underwater world making it ideal for scuba divers – in central Europe. Twelve metres of water covers trees, footpaths, benches and bridges that are usually accessible throughout the year. Visitors to the Green Lake in Tragoess, Austria, that is normally only one metre deep, can leisurely stroll around the picturesque lagoon. Photo: A diver crossing a bridge in the flood water. (Photo by Solnet/The Grosby Group)

Teeming with images of spectacular underwater scenes from around the world, Call of the Blue is the culmination of a five-year project by the photographer and ocean conservationist Philip Hamilton. This groundbreaking book includes contributions from acclaimed scientists and ocean “guardians”, who reveal what drove them to answer the call of the blue. (Photo by Philip Hamilton/The Guardian)