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.

John Waters / Shoal of Minnows (Phoxinus phoxinus) swimming and feeding in the River Wye, Wales, UK, July.

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.

Etienne Littlefair / Northern snapping turtles (Elseya dentata), small adult at rest amongst woody debris at the bottom of a deep creek bed in the Daly region, Northern Territory, Australia. June. Cropped.

Etienne Littlefair / White-throated snapping turtle (Elseya albagula), adult female with cataracts, found active, walking along the bottom of a rocky area in the Connors River, Queensland, Australia. August.

Etienne Littlefair / White-throated snapping turtle (Elseya albagula), large adult female with cataracts, found active, walking along the bottom of a deep pool in the upstream of the Mary River, Queensland, Australia. Aug...

Etienne Littlefair / Broad-shelled turtle (Chelodina expansa), adult actively moving along deep river bed, possibly foraging, Mary River, Queensland, Australia. July. Cropped.

Etienne Littlefair / Fitzroy river turtle (Rheodytes leukops), adult actively moving along the riverbed, Connors River, Queensland, Australia. August.

Etienne Littlefair / Fitzroy river turtle (Rheodytes leukops), adult actively moving along the riverbed, Connors River, Queensland, Australia. August. Cropped.

Etienne Littlefair / Fitzroy river turtle (Rheodytes leukops), adult actively moving along the rocky riverbed, Connors River, Queensland, Australia. August.

Etienne Littlefair / Mary river turtle (Elusor macrurus), full-sized adult male with alge-covered carapace heading for shelter under a fallen log, Mary River, Queensland, Australia. August.

Etienne Littlefair / Mary river turtle (Elusor macrurus), full-sized adult male walking along deep riverbed, Mary River, Queensland, Australia. August. Cropped.

Etienne Littlefair / Mary river turtle (Elusor macrurus), adult male walking along riverbed, with algae attached to his head, Mary River, Queensland, Australia. August. Cropped.

Etienne Littlefair / Mary river turtle (Elusor macrurus), juvenile resting, well-camouflaged, Mary River inland of Cambroon, Queensland, Australia. August.

Etienne Littlefair / Krefft's river turtle (Emydura macquarii krefftii), juvenile with carapace covered in algae, actively moving along riverbed of the Mary River, Queensland, Australia. August.

Etienne Littlefair / Krefft's river turtle (Emydura macquarii krefftii), adult actively moving along riverbed of the Mary River, Queensland, Australia. Cropped.

Etienne Littlefair / Gulf snapping turtle (Elseya lavarackorum), large adult female found active in deep water on a very hot summer night, Lawn Hill Creek, Queensland, Australia. January. Cropped.

Etienne Littlefair / Irwin's turtle (Elseya irwini), juvenile resting downstream of a riffle zone, North Johnstone River, downstream of Malanda, Far North Queensland, Australia. August. Cropped.

Etienne Littlefair / Irwin's turtle (Elseya irwini), juvenile swimming through submerged vegetation downstream of a riffle zone, North Johnstone River, downstream of Malanda, Far North Queensland, Australia. August. C...

Etienne Littlefair / Irwin's turtle (Elseya irwini), adult male resting. Note the sediment disturbance to the rear of the turtle is caused by expulsion of water via cloacal respiration. North Johnstone River, downstre...

Etienne Littlefair / Irwin's turtle (Elseya irwini), large adult female found actively moving around in a deep pool of the North Johnstone River, downstream of Malanda, Far North Queensland, Australia. August. Cropped...

Etienne Littlefair / Sandstone long-necked turtle (Chelodina burrungandjii) actively foraging at night, Pentecost River, Western Australia. April.

Etienne Littlefair / Saw-shelled turtle (Myuchelys latisternum), adult female resting, Townsville region, Queensland, Australia. September. Cropped. NOTE: some backscatter caused by photographer has been cloned out.

Ann & Steve Toon / Elephant (Loxodonta africana) in Shingwedzi river bed, Kruger National Park, South Africa.

Remi Masson / Group of Wels catfish (Silurus glanis) a tthe bottom of a river. River Loire, Indre-et-Loire, France. October.

Remi Masson / Group of Wels catfish (Silurus glanis) at the bottom of a river. River Loire, Indre-et-Loire, France. October.

Remi Masson / Giant wels catfish (Silurus glanis), longer than two meters, swimming above the bottom of the lake of Neuchatel, Switzerland.

Remi Masson / Common toads (Bufo bufo) in mating ball, Ain, Alps, France, April.

Robert Thompson / La Fraucata and Arazas River, Valle De Ordesa, Ordesa National Park, Spain. October 2019.

Robert Thompson / La Fraucata and Arazas River, Valle De Ordesa, Ordesa National Park, Spain. October 2019.

Robert Thompson / La Fraucata and Arazas River, Valle De Ordesa, Ordesa National Park, Spain. October 2019.

Orsolya Haarberg / Aerial view of an Arctic riverbed with sand banks and islands. Tana River, Norway. July.

Paul Hobson / White-clawed crayfish (Austropotamobius pallipes) on riverbed, Staffordshire, UK. September.

Paul Hobson / White-clawed crayfish (Austropotamobius pallipes) on riverbed, Staffordshire, UK. September.

Cyril Ruoso / Signal crayfish (Pacifastacus leniusculus), non-native invasive species. On riverbed in woodland. La Cure river, Morvan, Bourgogne-Franche-Comte, France. May.

Cyril Ruoso / Signal crayfish (Pacifastacus leniusculus), non-native invasive species, on riverbed. La Cure river, Morvan, Bourgogne-Franche-Comte, France. May.

Cyril Ruoso / Signal crayfish (Pacifastacus leniusculus), non-native invasive species, on riverbed in woodland. La Cure river, Morvan, Bourgogne-Franche-Comte, France. May.

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