Cyril Ruoso / Mute swan (Cygnus olor) feeding underwater, Burgundy, France, March.

Cyril Ruoso / Mute swan (Cygnus olor) feeding along riverbed, viewed underwater, Burgundy, France. November.

John Waters / Pair of Sea lampreys (Petromyzon marinus) spawning, one attempting to move a rock, River Wye, UK, June.

John Waters / Small group of Rainbow trout (Oncorhynchus mykiss) swimming in the River Kennet, Berkshire, England, UK, March.

John Waters / Small shoal of Brown trout (Salmo trutta) swimming and feeding in the River Kennet, Berkshire, England, UK, March.

Franco Banfi / Aquatic plants growing on bottom of the main spring at Rio Sucuri, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi,Franco Banfi / Piraputanga (Brycon hilarii) in the main spring Aqua¡rio Natural that goes in the Rio Bai­a Bonita, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Piraputanga (Brycon hilarii) reflecting on the water surface, Aqua¡rio Natural, Bonito, Mato Grosso do Sul, Brazil

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

Alex Mustard,Alex Mustard / A female (in front) and male Sockeye salmon (Oncorhynchus nerka) over eggs in their spawning river. Adams River, British Columbia, Canada, October.

Linda Pitkin / 2020VISION / Brown trout (Salmo trutta) fry on river bed, Cumbria, England, UK, September.

Michel Roggo / Sockeye / Red Salmon (Oncorhynchus nerka) on spawning migration; males surrounding a female. Adams River, British Columbia, Canada, October.

Paul Hobson / Signal crayfish (Pacifastacus leniusculus) on river bed near bridge, split level image. River Rivelin, Sheffield, England, UK. September 2018.

Paul Hobson / White-clawed crayfish (Austropotamobius pallipes) on riverbed, split level image. Staffordshire, England, UK. October.

Stephane Granzotto / Wels catfish (Silurus glanis), group on riverbed, River Loire, France. October.

Stephane Granzotto / Wels catfish (Silurus glanis), group on riverbed, River Loire, France. October.

Stephane Granzotto / Wels catfish (Silurus glanis) and Common carp (Cyprinus carpio), three on riverbed amongst branches, River Loire, France. October.

Stephane Granzotto / Wels catfish (Silurus glanis) and Common carp (Cyprinus carpio), three on riverbed amongst branches, River Loire, France. October.

Stephane Granzotto / Wels catfish (Silurus glanis), nine on riverbed, shoal of fish in background. River Loire, France. October.

Stephane Granzotto / Wels catfish (Silurus glanis) and diver, view from below. River Loire, France. October.

Stephane Granzotto / Wels catfish (Silurus glanis), five on riverbed, diver observing. River Loire, France. October.

Stephane Granzotto / Wels catfish (Silurus glanis), group above riverbed. River Loire, France. October.

Remi Masson / Group of Wels catfish (Silurus glanis) gathering on the bottom of the River Rhone, France. June.

Remi Masson / Group of Wels catfish (Silurus glanis) gathering on the bottom of the River Rhone, France. June.

Remi Masson / Giant wels catfish (Silurus glanis) sitting on the bottom of a river. Rio Ebro, Spain.

Remi Masson / Giant wels catfish (Silurus glanis) sitting on the bottom of a river. Rio Ebro, Spain.

Remi Masson / Wels catfish (Silurus glanis) on the bottom of the River Rhone, France. June.

Remi Masson / Wels catfish (Silurus glanis) amongst waterlilies. Lake of Paladru, Alps, Isere, France. June.

David Fleetham / Florida manatee (Trichechus manatus latirostris), four resting on sandy river bed. Split level image. Three Sisters Spring, Crystal River, Florida, USA.

David Fleetham / Florida manatee (Trichechus manatus latirostris), mother and calf on sandy river bed amongst fish. Three Sisters Spring, Crystal River, Florida, USA.

Michel Roggo / Sungai Melinau Paku River, long exposure underwater. Gunung Mulu National Park, Sarawak, Borneo, Malaysia. Photographed for The Freshwater Project.

Daniel Heuclin / Man catching African lungfish (Protopterus annectens annectens) buried in mud of dried river bed, Togo.

Daniel Heuclin / Man catching African lungfish (Protopterus annectens annectens) buried in mud of dried river bed, Togo.

Daniel Heuclin / West African lungfish (Protopterus annectens annectens) buried in mud of dried river bed, Togo.

Daniel Heuclin / Man catching African lungfish (Protopterus annectens annectens) buried in mud of dried river bed, Togo.

Nick Upton / Canary island date palm trees (Phoenix canariensis) beside dry river bed, Vega de Rio Palmas, Fuerteventura, Canary Islands, June.

Remi Masson / Shoal of Nase (Chondrostoma nasus) spawning, River Ain, Rhone-Alpes, France, April.

Remi Masson / Wels catfish (Silurus glanis) on the bottom of the River Rhone, France

Remi Masson / Wels catfish (Silurus glanis) sitting on the bottom of a river. Rio Ebro, Spain.

Remi Masson / European perch (Perca fluviatilis) in a river, River Ain, Alps, France

Remi Masson / Freshwater pearl mussel (Margaritifera margaritifera) on riverbed, Morvan Regional Nature Park, France, August. Endangered species.

Remi Masson / Chub (Squalius cephalus) on the bottom of a river, River Rhone, Alps, France

Remi Masson / Pumpkinseed (Lepomis gibbosus) in a lake. Savoie, Alps, France, July.

Remi Masson / European eel (Anguilla anguilla) in the River Rhone, Alps, France. Critically endangered species.

Remi Masson / Common nase (Chondrostoma nasus) in a river during the spawning, River Rhone, Alps, France

Remi Masson / Stone loach (Barbatula barbatula) in a river. Savoie, Alps, France.

Remi Masson / Brook lamprey (Lampetra planeri) mating in a river. Savoie, Alps, France

Remi Masson / Pyrenean brook salamander (Calotriton asper) under a small river. Pyrenees, Ariege, France, August.