David Fleetham / Hawksbill Turtle (Eretmochelys imbricata) and a shoal of fish near sea surface. Tubbataha Reef, Philippines.

Solvin Zankl / Baby Olive Ridley sea turtle (Lepidochelys olivacea) struggles against the swell to swim away from the beach where it hatched, Ostional, Costa Rica. October. Winner of the Underwater category of the G...

Alex Mustard / Southern stingray (Dasyatis americana) two swimming over sand bar, under stormy sky. Grand Cayman, Cayman Islands. British West Indies.

Doug Perrine / Dugong or Sea cow (Dugong dugon) split level view, Calauit Island, off Busuanga, Calamian Islands, Palawan, Philippines.

Alex Mustard / Split level image of Leather corals (Sarcophyton sp.) flourishing in shallow water close to uninhabited coral islands. Misool, Raja Ampat, West Papua, Indonesia. Ceram Sea. Tropical West Pacific Ocean...

Tui De Roy / Marine iguana (Amblyrhynchus cristatus), Punta Espinosa, Fernadina Island, Galapagos

David Fleetham / Humpback whale (Megaptera novaeangliae), mother and calf swimming just below surface in front of the West Maui Mountains. South of Lahaina, West Maui, Hawaii.

David Fleetham / Whale shark (Rhincodon typus), a commercial encounter for tourists with feeder above on canoe. Oslob, Cebu, Philippines. April 2017.

David Fleetham / Blacktip reef shark (Carcharhinus melanopterus) swimming just below surface at sunset, split level view. Off the island of Yap, Micronesia.

David Fleetham / Green Sea Turtle (Chelonia mydas) below surf instructor Tara Angioletti on a stand-up paddle board off Canoe Bearch, Maui, Hawaii. Model released.

Alex Mustard / Giant mottled eel (Anguilla marmorata) in river with villagers washing clothes in background. Ambon, Maluku Archipelago, Indonesia. Banda Sea, tropical west Pacific Ocean.

Alex Mustard / American crocodile (Crocodylus acutus) reflected in the surface as it floats, Jardines de la Reina, Gardens of the Queen National Park, Cuba. Caribbean Sea.

Alex Mustard / Southern stingray (Dasyatis americana) swimming over sand in shallow water, split level photo with blue sky and clouds. The Sandbar, Grand Cayman, Cayman Islands. British West Indies. Caribbean Sea.

Tui De Roy / Split level view of Brown pelicans (Pelecanus occidentalis) feeding, Tortuga Bay, Santa Cruz Island, Galapagos

Alex Mustard / Grey seal (Halichoerus grypus) split level of young seal investigating the camera with its nose and whiskers, close to shore. Lundy Island, Devon, UK, Bristol Channel. August

Alex Mustard / Grey seal (Halichoerus grypus) split level view of young investigating camera lens, Lundy Island, Devon, UK, Bristol Channel, August

Claudio Contreras / American crocodile (Crocodylus acutus) split level with animal resting at surface in shallow water over seagrass bed, Banco Chinchorro Biosphere Reserve, Caribbean region, Mexico

SCOTLAND: The Big Picture / Gannets (Morus bassanus) diving to feed on discarded fish, Shetland, Scotland, UK, April.

SCOTLAND: The Big Picture / Gannets (Morus bassanus) diving to feed on discarded fish, Shetland, Scotland, UK, April.

SCOTLAND: The Big Picture / Gannets (Morus bassanus) diving to feed on discarded fish, Shetland, Scotland, UK, April.

Tony Wu / Juvenile Australian sea lion (Neophoca cinerea) resting in shallows, possibly to thermoregulate, Carnac Island, Western Australia.

Luis Quinta / Body of deep sea squid floating near the surface, with mantle ripped up possibly by cetaceans such as Sperm whales which are present in the region, Pico Island, Azores, Portugal, May.

Alex Mustard / Scissortail sergeants (Abudefduf sexfasciatus) swimming over hard corals (Acropora sp.) on shallow reef at sunset, split level view. Gubal Island, Egypt. Red Sea.

Solvin Zankl / Portuguese man-of-war (Physalia physalis) colony, underwater Sargasso Sea, Bermuda

Juergen Freund / Banded sea kraits (Laticauda colubrina) around the roots of mangrove tree, split level. Mali Island, Macuata Province, Fiji, South Pacific.

Chris & Monique Fallows / Wandering albatross (Diomedea exulans), feeding and cleaning.

Ole Jorgen Liodden / Walrus (Odobenus rosmarus) underwater view, Edgeoya, Svalbard, Norway, June.

Jordi Chias / Juvenile Green turtle (Chelonia mydas) swimming near the surface, split level view, Fakarava atoll lagoon, Tuamotu Archipelago, French Polynesia, Pacific Ocean.

Jordi Chias / Juvenile Green turtle (Chelonia mydas) swimming near the surface, split level view, Fakarava atoll lagoon, Tuamotu Archipelago, French Polynesia, Pacific Ocean.

Jordi Chias / Juvenile green turtle (Chelonia mydas) reflected in the surface of the window with Snell's window affect, Fakarava atoll inside lagoon at sunset, Tuamotu archipelago, French Polynesia; Pacific Ocean

Alex Mustard / Southern stingray (Hypanus americanus) at the surface. Stingray City, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea. Bait was used for this shot.

Alex Mustard / Split level view of shallow coral reef in the Red Sea at sunset. Gordon Reef, Sinai, Egypt. Strait of Tiran, Gulf of Aqaba, Red Sea.

Michael Pitts / Green Turtle (Chelonia mydas) Hatchling swimming out to deep water from Karan Island after being released from boat. Saudi Arabia. Arabian Gulf.

Chris & Monique Fallows / Black browed albatros (Thalassarche melanophrys), Cape Point, South Africa.

Chris & Monique Fallows / Great white shark (Carcharodon carcharias) near surface, Seal Island, False Bay, South Africa.

Chris & Monique Fallows / Blue Shark (Prionace glauca) Cape Point, South Africa.

Willem Kolvoort / View of Byoutier. a very small island in the Seychelles with a pristine beach. Byoutier, Seychelles March 2005

Steven Kazlowski,Steven Kazlowski / Polar bear (Ursus maritimus) young bear in freezing water during autumn freeze up, Bernard Spit, 1002 area of the Arctic National Wildlife Refuge, North Slope, Alaska, Beaufort Sea

Michael Pitts / Lake Assal shoreline - Africas lowest point at 515 feet below sea level, Djibouti, , March 2008

Juergen Freund / Coral reef split level with mangroves with snorkeller, Raja Ampat, West Papua, Indonesia, February 2012 Model released.

Erlend Haarberg,Erlend Haarberg / Aerial view down river to the east of the Hofsjakull glacier and west of the Sprengisandur upland desert. Innumerable rivulets flow from beneath the glacier in this area of tundra which abounds in pon...

Michel Roggo / Grayling (Thymallus thymallus) on spawning ground. Lac de Fenetre, alpine lake, 2456 m above sea level, Canton of Valais, Switzerland, June.

Michel Roggo / Grayling (Thymallus thymallus) on spawning ground. Lac de Fenetre, alpine lake, 2456 m above sea level, Canton of Valais, Switzerland, June.

Mark Carwardine / California sealions (Zalophus californianus), one in water with other sitting on rock, Baja California, Sea of Cortez (Gulf of California), Mexico

Floris van Breugel / Turquoise waters of the lagoon along Ofu's National Park beach, American Samoa. January 2012.

Ole Jorgen Liodden / Male Hooker's / New Zealand sea lion (Phocarctos hookeri) in water, Campbell Island, New Zealand, sub Antarctic Islands. November.

Christophe Courteau / Mountain gorilla (Gorilla beringei) baby in mother's arms. 3000 metres above sea level in Volcanoes National Park, Rwanda. Short dry season, February

Christophe Courteau / Mountain Gorilla (Gorilla beringei) dominant male silver back sitting amongst vegetation. 2700 metres above sea level in Volcanoes National Park, Rwanda. short dry season, February

Nick Upton / Split level view of a Beadlet anemone (Actinia equina) attached to a boulder encrusted with Maerl (Lithothamnion glaciale) a red coralline alga, in a large rockpool, Crail, Scotland, UK, July

Terry Whittaker / 2020VISION / Water channels making patterns in saltmarsh, seen from the air. Abbotts Hall Farm, Essex, UK, April 2012. Did you know? Salt marshes are a great natural defence against sea level rise.

Bertie Gregory / 2020VISION / Avocet (Recurvirostra avosetta) silhouetted as its feeds at sunrise, Brownsea Island, Dorset, winter.

Terry Whittaker / 2020VISION / View of regenerated saltmarsh landscape around Abbots Hall Farm Nature Reserve at high tide, providing both a rich wildlife habitat and greater flood protection from sea level rise, Essex, England, UK...

Terry Whittaker / 2020VISION / Common glasswort (Salicornia europaea) growing on regenerated saltmarsh habitat, Abbotts Hall Farm Nature Reserve, Essex, England, UK, July

Terry Whittaker / 2020VISION / Saltmarsh at twilight, with lights of Bradwell-on-Sea in the background, Abbotts Hall Farm Nature Reserve, Essex, England, UK, July 2011

Alex Mustard / A split level view of shallow water and clouds in summer, Seven Mile Beach, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea.

Todd Mintz / Lemon shark (Negaprion brevirostris) at surface, Bahamas, Caribbean

Ole Jorgen Liodden / Galapagos Sea Lion (Zalophus wolllebaeki) under the surface. Galapagos

Nuno Sa / Blue Shark (Prionace glauca) at the sea surface. Santa Maria, Azores, August.

Nuno Sa / Blue Shark (Prionace glauca) at the sea surface. Santa Maria, Azores, August.

Nuno Sa / Blue Sharks (Prionace glauca) at the sea surface. Santa Maria, Azores, August.

Bryan and Cherry Alexander / Melting iceberg showing the portion underwater that is sculpted by the sea. Polar regions. Digitally created image composite

Bryan and Cherry Alexander / Tabular iceberg showing the portion underwater that is sculpted by the sea. Polar regions. Digitally created image composite

Bryan and Cherry Alexander / Ice arch iceberg showing the portion underwater that is sculpted by the sea. Polar regions. Digitally created image composite

Juergen Freund / Green turtles (Chelonia mydas) mating over coral reef, Sipadan Island, Sabah, Malaysia, June, Endangered species

Juergen Freund / Split level image of Papuan fisherman standing on his dugout canoe over shallow corals, New Ireland, Papua New Guinea, June 2010

Juergen Freund / Split level image of shallow bleaching corals at sunset, New Ireland, Papua New Guinea

Juergen Freund / Split level of solar powered gauge measuring sea temperature, West New Britain, Papua New Guinea, May 2010

Juergen Freund / Fisherman on outrigger boat catching Yellowfin tuna with hook and line. Sulawesi, Indonesia, December 2009. Fishermen fish close to a fish attracting device, some remain at sea for up to 2 months.

Juergen Freund / Split-level shot of coral reef and island. Misool, Raja Ampat, West Papua, Indonesia, January 2010

Juergen Freund / Local fishermen capturing a sea turtle for food, Kei islands, Moluccas, Indonesia, November 2009

Juergen Freund / Split-level shot of a shallow coral reef and house on stilts. North Raja Ampat, West Papua, Indonesia, February 2010

Juergen Freund / Papuan boy swimming in the shallows with his pet baby hawksbill turtle (Eretmochelys imbricata). Tunnung Island, New Hanover, Papua New Guinea, June 2010

Juergen Freund / Floating fruit of a Cannonball mangrove (Xylocarpus granatum) which when opened has seeds like a natural puzzle. Lembeh Strait, North Sulawesi, Indonesia, September 2009

Juergen Freund / Split-level shot of a pet baby Hawksbill turtle (Eretmochelys imbricata) swimming in the shallows. Tunnung Island, New Hanover, Papua New Guinea, June 2010.

Juergen Freund / Baby green turtle (Chelonia mydas) hatchling in the shallows of the beach, swimming out to sea. Anano Island, Wakatobi, South Sulawesi, Indonesia, November

Juergen Freund / Baby green turtle (Chelonia mydas) hatchling in the shallows of the beach, swimming out to sea. Anano Island, Wakatobi, South Sulawesi, Indonesia, November.

Juergen Freund / Split-level shot of Leatherback sea turtle (Dermochelys coriacea) baby swimming in the sea near the beach. Warmamedi beach, Bird's Head Peninsula, West Papua, Indonesia, July 2009

Juergen Freund / Split-level shot of Leatherback sea turtle (Dermochelys coriacea) with West Papuan boy in the water. Warmamedi beach, Bird's Head Peninsula, West Papua, Indonesia, July 2009

Juergen Freund / Split-level shot of Green turtle (Chelonia mydas) in the reef shallows, swimming towards the camera. Sipadan Island, Sabah, Malaysia, June

Juergen Freund / Split-level shot of mating pair of Green turtles (Chelonia mydas) in the reef shallows. Sipadan Island, Sabah, Malaysia, June

Juergen Freund / Split-level shot of Fan coral (Gorgonacea) in the shallows with boat shilouetted against the sunset in the background. North Raja Ampat, West Papua, Indonesia, February 2010

Juergen Freund / Split level shot of mating Green turtles (Chelonia mydas) in the reef shallows. Sipadan Island, Sabah, Malaysia, June

Alex Hyde / Dwarf snowbell (Soldanella pusilla) flower in snow. The plant generates heat by fermenting sugars to melt the surrounding snow. Austrian Alps, 2300 metres above sea level, June.

Alex Mustard / A split level view of a bull California sealion (Zalophus californianus) swimming beneath Los Islotes sealion colony. La Paz, Mexico. Sea of Cortez, East Pacific Ocean.

Alex Mustard / Portrait of a domestic pig (Sus domestica) sitting in the sea. Exuma Cays, Bahamas. Tropical West Atlantic Ocean. This family of pigs live on this beach in the Bahamas and enjoy swimming in the sea.

Alex Mustard / Split level view of a domestic pig (Sus domestica) bathing in the sea. Exuma Cays, Bahamas. Tropical West Atlantic Ocean. This family of pigs live on this beach in the Bahamas and enjoy swimming in t...

Alex Mustard / split level view of a domestic pig (Sus domestica) bathing in the sea. Exuma Cays, Bahamas. Tropical West Atlantic Ocean. This family of pigs live on this beach in the Bahamas and enjoy swimming in t...

Alex Mustard / Split level of female California sea lions (Zalophus californianus) basking in the sun on the surface. La Paz, Baja California Mexico. Sea of Cortez, East Pacific Ocean. October

David Woodfall / Family with their home threatened by rising sea level, Ganges delta, Bangladesh, July 2008

Juergen Freund / Richard Fitzpatrick releases Grey reef shark {Carcharhinus amblyrhynchos} after inserting transmitter into its belly, as part of the Coral Reef census, Lizard Island, Queensland, Australia, April 2008

Juergen Freund / Charlotte Watson snorkels down to collect sand which may contain polychaete worms, Coral Reef census, Lizard Island, Queensland, Australia, April 2008. Model released

Doug Allan / Humpback whale (Megaptera novaeangliae) swimming below a whale watching boat, Sue Flood, photographer in boat, Vava'u, Kingdom of Tonga, South Pacific, September 2006, Model released

Chadden Hunter / Dallol hot springs where water heated by magma laden with potassium, sulphur and iron spews up through salt pans staining the salt deposits with vivid colours, in the bottom of the Rift Valley, 120 me...

Tim Laman / Split level of Spotted sea hare {Aplysia dactylomela} on root of Red mangrove tree {Rhizophora mangle} where it was grazing on algae. Tunicate Cove, Belize.

Juergen Freund / Saltwater crocodile (Crocodylus porosus) swimming at water surface, split-level, New Guinea, Indo-pacific