Jordi Chias / Woman snorkeller swimming inside lagoon Toau atoll, Tuamotu Archipelago, French Polynesia, Pacific Ocean.

Christophe Courteau / African elephants (Loxodonta africana) swimming across Chobe River, trunks raised above surface for breathing, Chobe National Park, border between Botswana and Namibia.

David Pattyn / Children snorkelling in the sea and swimming with bottlenose dolphins (Tursiops truncatus) with boat approaching. Indian Ocean, Zanzibar, Tanzania, August 2014.

Angelo Gandolfi / Snorkeller with shoal of Piraputanga (Brycon hilarii), Rio Olha d'Agua at Cabeceira do Prata, Bonito, Mato Grosso do Sul, Brazil

Alex Mustard / A fisherman swims down to touch the statue of Christ Of The Abyss (Cristo degli abissi) for good fortune, in the Marine Protected Area of Portofino (Area Marina Protetta, Portofino), Liguria, Italy. M...

Franco Banfi / Two women snorkeling in front of the cave, Raja Ampat, Irian Jaya, West Papua, Indonesia, Pacific Ocean. Model released.

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

Mark Carwardine / Whale shark (Rhincodon typus) aerial view of juvenile with two people swimming alongside, La Paz Bay, Sea of Cortez (Gulf of California), Baja California, Mexico, March 2009

Alex Mustard / Whale shark (Rhincodon typus) silhouette of shark feeding on floating fish eggs (not visible) just below the surface in calm weather, with snorkeller taking photos nearby, Isla Mujeres, Quintana Roo,...

Todd Mintz / Scad fish / Horse mackerel (Trachurus trachurus) shoal with young male snorkeller, Bonaire, Dutch Caribbean. Model released.

Alex Mustard / 2020VISION / Snorkellers viewed from below, Kimmerage Bay, Dorset, UK, August

Alex Mustard / 2020VISION / A snorkeller in shallow, sunny waters, Man O War Bay, Jurassic Coast, Dorset, UK, August. Model released.

Juergen Freund / Mahonia Na Dari (Guardian of the Sea) Teacher Lorna Romaso leads a group of 16 students to snorkel and learn about the reef. West New Britain, Papua New Guinea, May 2010

Juergen Freund / Split-level shot of coral reef and island with snorkeller swimming underwater. Misool, Raja Ampat, West Papua, Indonesia, January 2010. Model released.

Juergen Freund / Diver amongst Sergeant major damselfish (Abudefduf vaigiensis) house reef of Miniloc Island Resort, El Nido, Palawan, Philippines. These fish come together densely when bread is thrown into the water...

Juergen Freund / Snorkeler swimming through a school of Oxeye scads (Selar boops) in the house reef of Miniloc Island Resort, El Nido island, Palawan, Philippines, May 2009. Model released.

Juergen Freund / Snorkeler swimming underwater, split level, with Miniloc Island Resort in the background, El Nido, Palawan, Philippines, May 2009. Model released

Alex Mustard / Female Grey seal (Halichoerus grypus) approaching a snorkeller's fins, Lundy Island, Devon, England, UK, North East Altantic Ocean. July 2010. Model released

Alex Mustard / Caribbean reef shark (Carcharhinus perezi) swimming over a coral reef, beneath a snorkeler and boat. Near Grand Bahama, Bahamas. Tropical West Atlantic Ocean.

Onne van der Wal / Young man snorkeling with a Green turtle (Chelonia mydas) in the Grenadines, Caribbean, February 2010. Model Released.

Onne van der Wal / Young man snorkeling over seagrass bed, holding a starfish, The Grenadines, Caribbean. February 2010, Model released.

Onne van der Wal / Young man snorkelling in the Exumas, Bahamas, Caribbean. June 2009, Model released.

Jeff Rotman / Snorkeler interacting with wild Bottlenose Dolphin (Tursiops truncatus), Nuweiba, Egypt - Red Sea. Model released Model released.

Juergen Freund / Person snorkelling over coral reef, Indo-Pacific

Alex Mustard / Snorkeller looking down on a Blue whale (Balaenoptera musculus) passing beneath. Indian Ocean, off Sri Lanka.

Franco Banfi / Snorkelling the tributary of the Paraguay River, Pantanal, Brazil

Franco Banfi / Photographer Franco Banfi snorkeling in search of fish in the Rio Sucuri, Bonito, Mato Grosso do Sul, Brazil

David Fleetham / Snorkeler diving in shallow water over hard coral reef. Two Tree Island near Kadavu Island, south east Fiji. November 2012. Model released.

Stephane Granzotto / Snorkeller taking pictures of Whale shark (Rhincodon typus) with tracking tag, Tadjourah Gulf, Republic of Djibouti. December, 2017.

Richard Robinson / Snorkeller at North Minerva Reef / Teleki Tokelau a disputed territory in the South Pacific between Tonga and Fiji. January 2015.

Richard Robinson / Snorkeller at North Minerva Reef / Teleki Tokelau a disputed territory in the South Pacific between Tonga and Fiji. January 2015.

Alex Mustard / Young Florida manatee (Trichechus manatus latirostris) plays with a snorkeller. Three Sisters Spring, Crystal River, Florida, USA.

Alex Mustard / Snorkeller rubbing the belly of a baby Florida manatee (Trichechus manatus latirostris). Three Sisters Spring, Crystal River, Florida, USA

Luis Quinta / Snorkeller in Blue shark (Prionace glauca) female off the coast of Portugal. August.

Juergen Freund / Woman swimming with Banded sea kraits (Laticauda colubrina) at low tide, Mali Island, Macuata Province, Fiji, South Pacific

Juergen Freund / Snorkellers swimming around Nudey Beach, Fitzroy Island, Tropical Far North Queensland, Australia. January 2016.

Juergen Freund / Snorkellers swimming around Nudey Beach, Fitzroy Island, Tropical Far North Queensland, Australia. January 2016.

Juergen Freund / Snorkellers swimming the reefs of the Great Barrier Reef, Queensland, Australia October 2016.

Juergen Freund / Snorkellers swimming the reefs of the Great Barrier Reef, Queensland, Australia October 2016.

Juergen Freund / Snorkellers swimming the reefs of the Great Barrier Reef, Queensland, Australia October 2016.

Juergen Freund / Aerial view of snorkellers swimming the reefs of the Great Barrier Reef, Queensland, Australia October 2016.

Juergen Freund / Aerial view of the reefs of the Great Barrier Reef showing the tourist dayboats, Great Barrier Reef, Queensland, Australia October 2016.

Juergen Freund / Aerial view of snorkellers swimming the reefs of the Great Barrier Reef, Queensland, Australia October 2016.

Juergen Freund / Split level of snorkellers swimming the reefs of the Great Barrier Reef underwater, Great Barrier Reef, Queensland, Australia October 2016.

Juergen Freund / Snorkellers swimming the reefs of the Great Barrier Reef with a semi-submesible carrying tourists to see the reef from underwater, Great Barrier Reef, Queensland, Australia October 2016.

Juergen Freund / Snorkellers swimming the reefs of the Great Barrier Reef with a semi-submesible carrying tourists to see the reef from underwater, Great Barrier Reef, Queensland, Australia October 2016.

Juergen Freund / Snorkellers swimming the reefs of the Great Barrier Reef with a semi-submesible carrying tourists to see the reef from underwater, Great Barrier Reef, Queensland, Australia October 2016.

Juergen Freund / Snorkeler videos the coral bleaching in the northern Great Barrier Reef. On 10 March 2017 the Great Barrier Reef Marine Park Authority confirmed mass coral bleaching is occurring on the Great Barrier...

Juergen Freund / Snorkeler videos the coral bleaching in the northern Great Barrier Reef. On 10 March 2017 the Great Barrier Reef Marine Park Authority confirmed mass coral bleaching is occurring on the Great Barrier...

Alex Mustard / Snorkeller swimming through Golden jellyfish (Mastigias sp.) in a marine lake, Jellyfish Lake, Eil Malk island, Rock Islands, Palau. Tropical north Pacific Ocean.

Alex Mustard / Woman snorkeling over a coral reef that is reflected on the surface. Sha'ab El Erg, Hurghada, Egypt. Red Sea. Model released.

Michel Roggo / Underwater view pf photographer Michel Roggo snorkelling in Anhumas Abyss Bonito area, Serra da Bodoquena (Bodoquena Mountain Range), Mato Grosso del Sul, Brazil. November 2012 . Photographed for The...

Michel Roggo / Photographer Michel Roggo snorkelling in the Sense river, Cantons of Fribourg and Bern, Switzerland. July. Photographed for The Freshwater Project.

Franco Banfi / Woman snorkeling near beach, Seychelles, Indian Ocean.

Franco Banfi / Woman snorkeling near a beach, Seychelles, Indian Ocean.

Inaki Relanzon / Green turtle (Chelonia mydas) swimming with snorkelers in the background, Canary Islands, Spain, July.

Alex Mustard / Two snorkellers swim in the water of a Cenote (a freshwater sink hole), while sun light filters down through the leaves of a red mangrove tree (Rhizophora mangle). Casa Cenote, Tulum, Quintana Roo Yuc...

Doug Perrine / Woman swimming with Hawaiian / Gray's Spinner Dolphins (Stenella longirostris longirostris), off Ho'okena Beach, South Kona, Hawaii, USA, Central Pacific Ocean. Model released

Pascal Kobeh / Snorkeler in front of the Arch among the rocky islands, Koror, Palau, Philippine Sea

Pascal Kobeh / Whale shark (Rhincodon typus) mouth wide open, feeding on plankton close to the surface with snorkelers nearby, Yucatan Peninsula, Mexico

Franco Banfi / Free diver swimming over a field of green algae moving in the current of Litlaa 'Little River', northern Iceland

Franco Banfi / Snorkeling over multicoloured sediments leaping from the bottom at Litlaaa 'Little River', northern Iceland

Tony Wu / Man holding up fresh Pygmy blue whale (Balaenoptera musculus brevicauda) faeces. The brilliant orange-red color derives from krill diet of the cetacean. Sri Lanka, Indian Ocean.

Alex Mustard / Snorkeller swimming over a shallow coral reef with a large stand of Staghorn coral (Acropora cervicornis). North Wall, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea. Critically enda...

Pete Oxford / Snorkeller collecting edible algae (Eucheuma sp.) Lighthouse Reef Atoll. Belize. May 2015.

Solvin Zankl / Algae scientist studying invasive Japanese wireweed (Sargassum muticum) Norway, May 2015.

Claudio Contreras / Freediver in sinkhole, Cenote Siete Bocas, near Puerto Morelos, Riviera Maya, Yucatan Peninsula, Mexico. April

Constantinos Petrinos / Young boy snorkelling over hard corals (reef-building corals) Sharm el Sheikh, Red Sea, Egypt, October 2010. Model released

Pascal Kobeh / Split level view of 'Barnacle' artificial reef with scuba diver. Built in 1997 with a steel frame using mild electric currents to encourage coral growth. Ihuru Island in North Male Atoll, Maldives,...

Pete Oxford / Cape gannet (Morus capensis) diving underwater with snorkelers behind,Eastern Cape, South Africa. Vulnerable. Endemic to Southern Africa

Pascal Kobeh / Bottlenose dolphins (Tursiops truncatus) swimming in open water with two snorkellers around them, Reunion Island. Indian Ocean. October 2009.

Pascal Kobeh / Young boy and an adult snorkeling at the surface above a group of spinner dolphins (Stenella longirostris) Egypt. Red Sea. June 2010.

Pascal Kobeh / Snorkler with a male green turtle (Chelonia mydas) Mayotte. Indian Ocean.

Michael Pitts / Tracking shot over bleached Table coral (Acropora) towards a man snorkelling, Maldives, Indian Ocean.

Franco Banfi / Photographer Franco Banfi snorkelling in search of fish in the Rio Sucuri, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Woman snorkeling at Rukavac beach, Vis Island, Croatia, Adriatic Sea, Mediterranean

Franco Banfi / Woman snorkeling in front of the beach of Komiza, Vis Island, Croatia, Adriatic Sea, Mediterranean

Franco Banfi / Woman snorkeling in front of the beach of Komiza, Vis Island, Croatia, Adriatic Sea, Mediterranean

Franco Banfi / Two women snorkeling in front of the cave, Raja Ampat, Irian Jaya, West Papua, Indonesia, Pacific Ocean

Franco Banfi / Shoal of Powder blue surgeonfish (Acanthurus leucosternon) swimming over reef, with snorkeller in background, Maldives, Indian Ocean

Franco Banfi / Shoal of Powder blue surgeonfish (Acanthurus leucosternon) swimming over reef, with snorkeller in background, Maldives, Indian Ocean

Michele Westmorland / Snorkeler swimming with harmless Jellyfish (Mastigias papua etpisonii), Jellyfish Lake, Rock Islands, Palau, Micronesia model released

Richard Du Toit / African Elephant (Loxodonta africana) totally submerged underwater with just tip of trunk above water, Limpopo Province, Kruger National Park, South Africa

Alex Mustard / A snorkeller films himself swimming with a filter feeding Whale shark (Rhincodon typus), Isla Mujeres, Quintana Roo, Yucatan Peninsula, Mexico, Caribbean Sea.

Mark Carwardine / Whale shark (Rhincodon typus) aerial view of juvenile with man swimming, La Paz Bay, Sea of Cortez (Gulf of California), Baja California, Mexico, March 2009

Mark Carwardine / Whale shark (Rhincodon typus) aerial view of juvenile with five people swimming / snorkelling behind, La Paz Bay, Sea of Cortez (Gulf of California), Baja California, Mexico, March 2009

Mark Carwardine / Snorkellers tied to rope attached to boat, whale watching in strong current, Ribbon Reefs, Great Barrier Reef, Queensland, Australia

Mark Carwardine / Dwarf minke whale {Balaenoptera acutorostrata} (possible sub-species of common Minke whale) surfacing near to a whale watching snorkeller who is tied to rope attached to boat in strong current, Ribbon...

Mark Carwardine / Snorkellers tied to rope attached to boat, whale watching in strong current, Ribbon Reefs, Great Barrier Reef, Queensland, Australia

Mark Carwardine / Dwarf minke whale {Balaenoptera acutorostrata} (possible sub-species of common Minke whale) surfacing near to a whale watching snorkeller who is tied to rope attached to boat in strong current, Ribbon...

Alex Mustard / Whale shark (Rhincodon typus) feeding, open mouthed, on fish eggs (not visible) at the surface, with a snorkeller watching. Isla Mujeres, Quintana Roo, Yucatan Peninsular, Mexico, Caribbean Sea.

Alex Mustard / Whale shark (Rhincodon typus) feeding on fish eggs (visible as white blobs) at the surface in calm weather, with snorkeller behind. Isla Mujeres, Quintana Roo, Yucatan Peninsular, Mexico. Caribbean Se...

Todd Mintz / Young man snorkelling next to dense shoal of Scad fish / Horse mackerel (Trachurus trachurus) Bonaire, Dutch Caribbean.

Todd Mintz / Person snorkelling next to dense shoal of Scad fish / Horse mackerel (Trachurus trachurus) Bonaire, Dutch Caribbean.