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

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.

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

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

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