Under Exposed: Pekka Tuuri (Finland) – Great white shark, Isla Guadalupe, Mexico. “Isla Guadalupe is the world capital when it comes to observing great white sharks, but cage diving seriously limits the possibilities to take ‘fresh’ pictures. When I took this, the water close to the surface was quite milky, making photography very challenging. From out of the “mist”, I saw this great white shark lurking behind a school of fusiliers. I quickly focused on the shark and set a wide aperture to get focus blur on the fish, along with a fast shutter to avoid excessive motion blur”. (Photo by Pekka Tuuri/The Outdoor Photographer of the Year/The Guardian)

The Florida Keys are famous for their diving, but they are less well known for another quirky attraction: the mailboxes residents use to decorate their driveways. From a fiberglass manatee in lipstick to a small white church, Reuters photographer Wolfgang Rattay documented this unusual aspect of local culture as he drove along the Ocean Highway that connects the islands. Photo: A mailbox in the shape of a fire truck is seen along the highway US-1 in the Lower Keys near Marathon in Florida, July 11, 2014. (Photo by Wolfgang Rattay/Reuters)

Californian photographer and conservationist Octavio Aburto had spent years photographing the school in Cabo Pulmo National Park, Mexico – and had been trying to capture this exact shot for three years. “Together with my friend David Castro, we were diving with a large group of Bigeye travellies at Cabo Pulmo National Park, Mexico. Thousands of fish forming a ball during the reproduction courtship. In the afternoon, these fish congregate to form a large spawning aggregation around the reefs of the National Park”. (Photo and caption by Octavio Aburto)

“Alice in Waterland” is a beautiful series of photographs re-imagining the Lewis Carroll classic underwater. It’s a creation of photographer Elena Kalis, who lives on a small island in The Bahamas, surrounded, she says, “by pristine clear warm water. Underwater is where I spend a lot of time; snorkeling, diving, photographing. It is fascinating how the world changes down below: light, sound, gravity and proportions are different from what we are used to”. (Photo by Elena Kalis)

Tom Wilder, 17 from Kent, dives in the mud at the Glastonbury Festival site at Worthy Farm, Pilton on June 23, 2011 in Glastonbury, England. Music fans had to brave more rain today at the five-day festival which opened yesterday. This year the festival will feature headline acts U2, Coldplay and Beyonce. The festival, which started in 1970 when several hundred hippies paid 1 GBP to watch Marc Bolan, has grown into Europe's largest music festival attracting more than 175,000 people over five days. (Photo by Matt Cardy/Getty Images)

Cave Diver, Anhumas Abyss, Bonito, Brazil: The Anhumas Abyss is an underground cavern with a crystal-clear lake below, more than 260 feet (79 m) deep. A visitor must enter through a narrow opening at the top of the chamber and rappel into the cave. Snorkeling and scuba diving in the lake reveal amazing scenery. Distinctive, conical limestone stalagmites and stalactites occupy the lake and the surrounding area, some reaching 65 feet (20 m) high. (Photo by Marcio Cabral/Nature’s Best Photography Awards 2017)

It looks like an underwater tornado, but a diver was actually stuck in the middle of a huge school of fish. The fish swarmed around Mika Woyda in their thousands as she swam off the coast of Cabo Pulmo, Mexico. Her husband Caine Delacy snapped the breath-taking images of Mika in scenes he revealed he had never witnessed in 20 years of diving. Before entering the water the couple, who live in Boulder, Colorado, had some shots in mind but never imagined what they would capture. Here: photographer Caine Delacy with his wife Mika Woyda. (Photo by Caine Delacy/Mika Woyda/Caters News)

Jellyfish Lake (Palauan: Ongeim'l Tketau, “Fifth Lake”) is a marine lake located on Eil Malk island in Palau. Eil Malk is part of the Rock Islands, a group of small, rocky, mostly uninhabited islands in Palau's Southern Lagoon, between Koror and Peleliu. There are about 70 other marine lakes located throughout the Rock Islands. Jellyfish Lake is one of Palau's most famous dive (snorkeling only) sites. It is notable for the millions of golden jellyfish which migrate horizontally across the lake daily.