Jordi Chias / Jellyfish (Diplulmaris antarctica) Cuverville, Antarctic Peninsula, Antarctica.

Jordi Chias / Weddell seal (Leptonychotes weddellii), Antarctic Peninsula, Antarctica.

Franco Banfi / Freshwater fish including Mayan cichlids (Mayaheros urophthalmus) between aquatic plants and leaves, Cenote Nicte-Ha, near Tulum, Quintana Roo, Yucatan Peninsula, Mexico. MontPhoto Competition 2023 -...

Michel Roggo / Autumn trees viewed from below Lake Baikal, Lake Baikal UNESCO World Heritage Site, Siberia, Russia. May 2013. Photographed for The Freshwater Project.

Alex Mustard / Aggregation of Golden jellyfish (Mastigias sp.) in a marine lake in Palau, the golden colour of this species comes from symbiotic algae in its tissues. Jellyfish Lake, Eil Malk island, Rock Islands, P...

Claudio Contreras / Morelet's crocodile (Crocodylus moreletii) in sinkhole, Cenote Carwash, near Tulum, Yucatan Peninsula, Mexico, January

Claudio Contreras / Green turtle (Chelonia mydas) wide angle view of fin, Akumal, Caribbean Sea, Mexico, January. Endangered species.

Claudio Contreras / Mesoamerican slider turtle / terrapin (Trachemys scripta venusta) in sinkhole, Cenote Carwash, near Tulum, Yucatan Peninsula, Mexico, January

Claudio Contreras / Morelet's crocodile (Crocodylus moreletii) in sinkhole, Cenote Carwash, near Tulum, Yucatan Peninsula, Mexico, January

Richard Robinson / Blue shark (Prionace glauca) just below surface, Hauraki Gulf, Auckland, New Zealand, June.

Franco Banfi / California sea lion (Zalophus californianus), Los Islotes, Sea of Cortez, Baja California peninsula, Mexico, East 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

Jordi Chias / Green turtle (Chelonia mydas) from underneath swimming through the surface, Mayotte Island, Comores, Indian Ocean.

Jean E. Roche / Giant mirror in the shape of a woman emerging from river, a public sculpture by Rob Mullholland, Port Saint Louis du Rhone, Camargue, France, May 2013. Editorial Use only. Credit Jean Roche / Le Citro...

Jean E. Roche / Woman looking into giant 'funhouse' mirror in forest, public sculpture by Rob Mullholland, Port saint Louis du Rhone, Camargue, France, May 2013. Editorial Use only. Credit Jean Roche / Le Citron Jaun...

Wild Wonders of Europe / Lundgren / Pool Frog (Pelophylax lessonae) viewed from below while swimming, underwater around Crisan village, Danube Delta, Romania, June.

Michel Roggo / Brown bear (Ursus arctos beringianus) fishing for Sockeye salmon in the Ozernaya River, Kamtchatka, Russia, August

Orsolya Haarberg / Northern fulmar (Fulmarus glacialis) below a black-legged kittiwake (Rissa tridactyla). The optical phenomenon, caused by a backscattering of light, is called a glory. Hornstrandir Nature Reserve, Ice...

Erlend Haarberg / Northern fulmar (Fulmarus glacialis) with optical glory phenomenon in mist, Hornvik, Hornstrandir Nature Reserve, West Fjords, Iceland, July 2008

Tony Heald / Circle round the sun, optical effect of high level ice crystals, around midday, Chobe NP, Botswana

Jordi Chias / Jellyfish (Diplulmaris antarctica) Cuverville, Antarctic Peninsula, Antarctica.

Alex Mustard / A marine iguana (Amblyrhynchus cristatus) silhouetted at the surface. Cape Douglas, Fernandina Island, Galapagos National Park, Galapagos Islands. East Pacific Ocean.

Alex Mustard / Shallow, turquiose water and the surface, with blue sky. Raja Ampat, West Papua, Indonesia. Dampier Strait. Ceram Sea. Tropical West Pacific Ocean.

Michel Roggo / Underwater view of African tigerfish (Hydrocynus vittatus), predatory fish in the Okavango river with Water lily (Nymphaea nouchali var. caerulea) and other aquatic plants. Okavango Delta, Botswana,...

Michel Roggo / Etang de la Gruere, peat bog, with red tannin water, Rhine river catchment, Canton of Jura, Switzerland. November. Photographed for The Freshwater Project

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...

Alex Mustard / Sun light filters down through the leaves of a Red mangrove tree (Rhizophora mangle). Casa Cenote, Tulum, Quintana Roo, Yucatan, Mexico.

Alex Mustard / Shallow ocean scene, sun patterns on sand, surface and sky. Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea

Yva Momatiuk & John Eastcott / Impala (Aepyceros melampus) male at waterhole, with reflection of another male creating an optical illusion, Etosha National Park, Namibia

Yva Momatiuk & John Eastcott / Impala (Aepyceros melampus) females drinking at waterhole in dry season, with reflection of male creating an optical illusion, Etosha National Park, Namibia

Cyril Ruoso / Common minnow (Phoxinus phoxinus) group in Massane river. Alberes Mountains, Pyrenees, France, October.

Cyril Ruoso / Common minnow (Phoxinus phoxinus) group in Massane river. Alberes Mountains, Pyrenees, France, October.

Franco Banfi / Galapagos sea lion (Zalophus californianus) in water. Galapagos Islands, East Pacific Ocean.

Franco Banfi / Galapagos sea lion (Zalophus californianus) in water. Galapagos Islands, East Pacific Ocean.

Claudio Contreras / Green turtle (Chelonia mydas) wide angle view, Akumal, Caribbean Sea, Mexico, January. Endangered species.

Claudio Contreras / Green turtle (Chelonia mydas) close up, wide angle view from below, Akumal, Caribbean Sea, Mexico, January. Endangered species.

Claudio Contreras / Green turtle (Chelonia mydas) swimming down from surface, Akumal, Caribbean Sea, Mexico, January. Endangered species.

Claudio Contreras / Green turtle (Chelonia mydas) swimming down from surface, Akumal, Caribbean Sea, Mexico, January. Endangered species.

Claudio Contreras / Morelet's crocodile (Crocodylus moreletii) in sinkhole, Cenote Carwash, near Tulum, Yucatan Peninsula, Mexico, January, DE

Claudio Contreras / Mesoamerican slider turtle / terrapin (Trachemys scripta venusta) in sinkhole, Cenote Carwash, near Tulum, Yucatan Peninsula, Mexico, January

Claudio Contreras / Morelet's crocodile (Crocodylus moreletii) in sinkhole, Cenote Carwash, near Tulum, Yucatan Peninsula, Mexico, January

Alex Mustard / Southern stingray (Hypanus americanus) swimming over a sand bar in the early morning. Grand Cayman, Cayman Islands. Caribbean Sea.

Richard Robinson / A Blue shark (Prionace glauca) just below the surface, with nictitating membrane partially shut to protect its eye, Hauraki Gulf, Auckland, New Zealand, June.

Richard Robinson / Blue shark (Prionace glauca) just below surface, Hauraki Gulf, Auckland, New Zealand, June.

Michel Roggo / Underwater view of aquatic plants in Wadi Shab, or Wadi Al Shab, Al Sharqiyah South Governorate, Sultanate of Oman. February 2015. Photographed for The Freshwater Project

Franco Banfi / California sea lions (Zalophus californianus) underwater, Los Islotes, Sea of Cortez, Baja California, Mexico, East Pacific Ocean.

Pete Oxford / Pearl farming lines underwater, J Hunter Pearl Farm, Savusavu island, Fiji, South Pacific, April 2014. Fiji is known for producing 'black' pearls.

Franco Banfi / Partly submerged ruins viewed through Snell's window, Lago di Capo D'Acqua, Capestrano, Aquila, Abruzzo, Italy, May 2006.

Willem Kolvoort / Yellow waterlily (Nuphar lutea) seen from underwater in brook, North Holland. June.

Willem Kolvoort / Purple marshlocks (Potentilla palustris) viewed from underwater, central Holland. May.

Pascal Kobeh / Three Short-finned pilot whales (Globicephala macrorhynchus) close to the surface against the light, Costa Rica. Pacific ocean.

Pascal Kobeh / Three Short-finned pilot whales (Globicephala macrorhynchus) close to the surface against the light, Costa Rica. Pacific ocean.

Bert Willaert / School of young European perch (Perca fluviatilis) in Altausseer lake, Austria, July.

Alex Mustard / School of Blackfin barracuda (Sphyraena qenie) are framed against Snell's Window. Waigeo, Raja Ampat, West Papua Indonesia. Dampier Strait, Tropical West Pacific Ocean.

Michel Roggo / Underwater view of aquatic plants in oxbow lake on the shore of Lake Baikal, UNESCO World Heritage Site.Irkutsk Oblast, Siberia, Russia, September 2013. Taken for the Freshwater Project.

Michel Roggo / Snell's window effect through Wadi Shawka (or Shoqwa, Shaqwa), Ras al Kaimah, United Arab Emirates, November 2010. Taken for the Freshwater Project.

Michel Roggo / Atlantic salmon (Salmo salar) in holding pool on upstream spawning migration, Quebec, Canada, August. Taken for the Freshwater Project.

Luis Quinta / Blue shark (Prionace glauca) Faial Island, Azores, Portugal, Atlantic Ocean, September.

Robin Chittenden / Boy looking at leaf through magnifying glass, Norwich, UK, November 2013. Model released.

Aflo / Shoal of fish, Carnac Island, Perth, Australia.

Jean E. Roche / Giant mirror in the shape of a person, a public sculpture by Rob Mullholland, Port Saint Louis du Rhone, Camargue, France, May 2013. Editorial Use only. Credit Jean Roche / Le Citron Jaune / Mullholla...

Jean E. Roche / Giant mirror in the shape of a person, a public sculpture by Rob Mullholland, Port Saint Louis du Rhone, Camargue, France, May 2013. Editorial Use only. Credit Jean Roche / Le Citron Jaune / Mullholla...

Jean E. Roche / Man (assistant to the artist) looking into giant mirror in the shape of a person, a public sculpture by Rob Mullholland, Port Saint Louis du Rhone, Camargue, France, May 2013. Editorial Use only. Cred...

Jean E. Roche / Giant mirror in the shape of a woman emerging from river, a public sculpture by Rob Mullholland, Port Saint Louis du Rhone, Camargue, France, May 2013. Editorial Use only. Credit Jean Roche / Le Citro...

Jean E. Roche / Man looking into giant 'funhouse' mirror in forest, public sculpture by Rob Mullholland, Port saint Louis du Rhone, Camargue, France, May 2013. Editorial Use only. Credit Jean Roche / Le Citron Jaune...

Jean E. Roche / Woman looking into giant 'funhouse' mirror in forest, public sculpture by Rob Mullholland, Port saint Louis du Rhone, Camargue, France, May 2013. Editorial Use only. Credit Jean Roche / Le Citron Jaun...

Wild Wonders of Europe / Lundgren / School of Belica fish (Leucaspius delineatus) at the edge of a Soft hornwort carpet (Ceratophyllum submersum), Danube, Danube Delta, Romania, June.

Wild Wonders of Europe / Lundgren / Water chestnut (Trapa natans) viewed from underwater, in Danube Delta, Romania, June.

Wild Wonders of Europe / Lundgren / Water chestnut (Trapa natans) viewed from underwater, in Danube Delta, Romania, June.

Wild Wonders of Europe / Lundgren / Pool Frog (Pelophylax lessonae) viewed from below while swimming, underwater around Crisan village, Danube Delta, Romania, June.

Wild Wonders of Europe / Lundgren / European white waterlilies (Nymphaea alba) viewed from underwater in a tributary of Danube Delta, Romania, June.

Wild Wonders of Europe / Widstr / Vlado Peikov, hunting area manager, with binoculars, Deven area, Western Rhodope Mountains, Bulgaria, May 2013.

Wild Wonders of Europe / Widstr / Vlado Peikov, hunting area manager looking through binoculars, Deven area, Western Rhodope Mountains, Bulgaria, May 2013.

Wild Wonders of Europe / Widstr / Ranger and field officer Todor Mitkov with binoculars, Plevun, Eastern Rhodope Mountains, Bulgaria, May 2013.

Nick Garbutt / Man enjoying the view from the peak of Marojejy Summit (2133m), Marojejy National Park, north eastern rainforest region, Madagascar.

Alex Mustard / Old tree branches on the floor of Cenote pool, beneath the forest canopy with Snell's Window effect. Puerto Aventuras, Quintana Roo, Mexico.

Solvin Zankl / GEOMAR / Coral (Madrepora oculata) in respiration chambers where scientists determine oxygen consumption using optical sensors, Norway, September 2011. Photo taken in cooperation with GEOMAR coldwater coral r...

Bruno D'Amicis / Optical "glory" phenomenon and photographer's shadow. High Tatras, Slovakia, June.

Alan Watson / Slug with optical tentacles extended, on the trunk of a Mango tree (Mangifera indica) at 400 metres, near Loma Quita Espuela Scientific Reserve, Dominican Republic

Yva Momatiuk & John Eastcott / Blue Flash, rare optical phenomenon of refraction of light spectrum when air is clear, briefly visible on horizon of Pacific Ocean at sunset, winter, South Island, New Zealand

Tony Heald / Circle round the Sun, optical effect of high level ice crystals, around midday, Chobe NP, Botswana.

Kim Taylor / Sunlight shining through trees, split into red green + blue by filter on camera lens.

Franco Banfi / Water hyacinth (Eichhornia sp.) in flower underwater, Pantanal, Mato Grosso, Brazil.

Franco Banfi / RF - Spectacled caiman (Caiman crocodilus) underwater portrait, Pantanal, Mato Grosso, Brazil. (This image may be licensed either as rights managed or royalty free.)

David Fleetham / Lionfish (Pterois volitans) swimming over coral reef, Indonesia, Indo-Pacific.

Shane Gross / Whale shark (Rhincodon typus) swimming close to surface accompanied by three Pilot fish (Naucrates ductor) with snorkeler swimming above, La Ventana, Baja California, Sea of Cortez, Mexico. Endangered...

Shane Gross / Munk's devil rays (Mobula munkiana) large shoal aggregating underwater, La Ventana, Baja California, Mexico, Sea of Cortez.

Shane Gross / Munk's devil rays (Mobula munkiana) large shoal aggregating underwater, La Ventana, Baja California, Mexico, Sea of Cortez.

Shane Gross / California sea lion (Zalophus californianus) swimming close to surface of sunlit ocean, Los Islotes, Baja California Sur, Mexico, Sea of Cortez.

Lewis Jefferies / Compass jellyfish (Chrysaora hysoscella) drifting close to surface with bright sunshine and blue sky above, Falmouth, Cornwall, UK, Atlantic Ocean.

Lewis Jefferies / Grey seal (Halichoerus grypus) swimming in shallow water with blue sky above, Lundy Island, Bristol Channel, Devon, UK.

Alex Mustard / Soft corals (Dendronephthya sp. and Scleronephthya sp.) on the underside of a reef, beneath sun beams, Raja Ampat, West Papua, Ceram Sea, Pacific Ocean.

Alex Mustard / Green turtle (Chelonia mydas) surfacing, lifting its head to breathe, Raja Ampat, West Papua, Ceram Sea, Pacific Ocean. Endangered.

Alex Mustard / Leather coral (Sarcophyton sp.) framed in Snell's window, Tubbataha Atolls, Palawan, Philippines, Sulu Sea.

Alex Mustard / Table coral (Acropora sp.) growing on a reef wall, Tubbataha Atolls, Palawan, Philippines, Sulu Sea.