Martin Willis / Mangroves along coast and boat, Deluge Inlet, Hinchinbrook Island National Park, Queensland, Australia

Milan Radisics / Aerial shot of the estuary of the Holmsa and Kudafljot glacial rivers, Grafarkirkja, Iceland, August 2018.

Colin Monteath/ Hedgehog House / Purakaunui Falls, Catlins, New Zealand

Marion Vollborn/ BIA / Leopard (Panthera pardus) cub, Okavango Delta, Botswana

Andres M. Dominguez/ BIA / Common Tern (Sterna hirundo) flying with fish prey, Danube Delta, Romania

Jeff Foott / Mountains and river after autumn snowfall, Sunwapta River, Jasper National Park, Alberta, Canada

Jeff Foott / Sunwapta Falls, Sunwapta River, Jasper National Park, Alberta, Canada

Jeff Foott / Sunwapta Falls, Sunwapta River, Jasper National Park, Alberta, Canada

Jeff Foott / Mountain Dogwood (Cornus nuttallii) flowering, Merced River, Yosemite National Park, California

Jeff Foott / Mountain Dogwood (Cornus nuttallii) flowering, Merced River, Yosemite National Park, California

Jeff Foott / Mountain Dogwood (Cornus nuttallii) flowering, Merced River, Yosemite National Park, California

Jeff Foott / Mountain Dogwood (Cornus nuttallii) flowering, Merced River, Yosemite National Park, California

Jeff Foott / Little Missouri River, Theodore Roosevelt National Park, North Dakota

Jeff Foott / Mountain Dogwood (Cornus nuttallii) flowering, Merced River, Yosemite National Park, California

Jeff Foott / Yosemite Falls and Merced River, Yosemite National Park, California

Paul Souders/ Worldfoto / Black Heron (Egretta ardesiaca) canopy hunting, Chobe River, Chobe National Park, Botswana

Chase Dekker / Brown Bear (Ursus arctos) in river, Katmai National Park, Alaska

Anup Shah / African Elephant (Loxodonta africana) herd crossing river, Masai Mara, Kenya

Tim Fitzharris / Conifers and Lower Yellowstone Falls, Yellowstone River, Grand Canyon of Yellowstone, Yellowstone National Park, Wyoming

Vincent Grafhorst / Minden / River in sandstone cave, Sof Omar Cave, Ethiopia

David Fleetham / Florida manatee (Trichechus manatus latirostris) at Three Sisters Spring in Crystal River, Florida, USA.

David Fleetham / Florida Manatee (Trichechus manatus latirostris), Three Sisters Spring, Crystal River, Florida, USA. National Wildlife Federation Photo Contest Grand Prize WINNER 2010.

Chien Lee / Giant Crab Spider (Sparassidae) feeding on tree frog prey, Digul River, Papua, Indonesia

Yva Momatiuk & John Eastcott / Canoe on river in summer, Hudson River, Hudson Gorge Wilderness, New York

Kirkendall-Spring Photographers / Vicky Spring next to a small tarn, Lyman Lakes Basin, Glacier Peak Wilderness, Wenatchee National Forest, Washington, USA, September 2014. Model released.

Yva Momatiuk & John Eastcott / Rhyolite mountains and geothermal vents, Kerlingarfjoll, Iceland

Yva Momatiuk & John Eastcott / River with waterfalls in tundra, Klifbrekkufossar Waterfall, Mjoifjordur, Iceland

Chien Lee / Spike-browed Frog (Sphenophryne cornuta) father transporting froglets, Digul River, West Papua, Indonesia

Chien Lee / Spike-browed Frog (Sphenophryne cornuta) father transporting froglets, Digul River, West Papua, Indonesia

Mark Raycroft / Elk (Cervus elaphus) bull in river in mist, North America

Paul Bertner / Forest-covered hills and river, Taironaka Lodge, Colombia

Marion Vollborn/ BIA / African Lion (Panthera leo) cubs drinking at waterhole, Okavango Delta, Botswana

Michel Roggo / Atlantic salmon (Salmo salar) migrating upstream to spawn, Quebec, Canada Photographed for the Freshwater Project.

Jeff Foott / Waterfall and river in canyon, Calf Creek Falls, Grand Staircase-Escalante National Monument, Utah

Jeff Foott / Trees in fall near Calf Creek Falls, Grand Staircase-Escalante National Monument, Utah

Ingo Arndt / Tisza mayflies (Palingania longicauda) swarming, River Tisza, Hungary, June

Ingo Arndt / Tisza mayfly (Palingania longicauda) hanging on branch and moulting, River Tisza, Hungary, June

Ingo Arndt / Mayflies (Palingenia longicauda) swarming, Tisza river, Hungary, June

Ingo Arndt / Mayfly (Palingenia longicauda) on water surface, swarming, Tisza river, Hungary, June

Ingo Arndt / Brown / Grizzly Bear (Ursus arctos horribilis) female with two cubs crossing river, Alaska, USA

Ingo Arndt / Aerial view of the "American Falls / Horseshoe Falls", Niagara Falls, North America

Ingo Arndt / Aerial view of "American Falls / Horseshoe Falls", Niagara Falls, North America

Ingo Arndt / Aerial view of the "American Falls", Niagara Falls, New York, USA

Ingo Arndt / Yosemite Falls flowing strong with water, Yosemite NP, California, USA

Ingo Arndt / White water river rapids, Salto Grande, Torres del Paine NP, Patagonia, Chile

Tim Fitzharris / Half Dome reflecting in Merced River, Yosemite National Park, California

Hiroya Minakuchi / Japanese Firefly (Luciola cruciata) group flying along river at night, Shikoku, Japan

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

Sam Hobson / Red fox (Vulpes vulpes) vixen in front of Clifton Suspension Bridge at night. Avon Gorge, Bristol, UK. March 2016.

Sebastian Kennerknecht / Snow Leopard (Panthera uncia) wild female, wet after having crossed river, in mountain valley, Uchkul River, Sarychat-Ertash Strict Nature Reserve, Tien Shan Mountains, eastern Kyrgyzstan

Laurent Geslin / European beaver (Castor fiber) at river bank in urban environment at night, Grenoble, France, August.

Nick Hawkins / Neotropical river otter (Lontra longicaudis) in water, Nicoya Peninsula, Costa Rica, March 2015.

Danny Green / Coastal brown bear (Ursus arctos) fishing, Lake Clarke National Park, Alaska, September

Tim Fitzharris / River in gorge, Rio Grande Gorge, Rio Grande del Norte National Monument, New Mexico

Yashpal Rathore / Asiatic elephant (Elephas maximus), herd drinking water and crossing Mountain River at dawn, Jim Corbett National Park, India.

Andy Rouse / African Leopard (Panthera pardus) jumping across river Maasai Mara, Kenya, Africa. August.

Ann & Steve Toon / Atlantic salmon (Salmo salar) leaping on upstream migration, River Tyne, Hexham, Northumberland, UK, November

Tony Heald / Giant Otter (Pteronura brasiliensis) adult with young in water, Pantanal, Brazil

Sergey Gorshkov / Aurora borealis over river, Putoransky State Nature Reserve, Putorana Plateau, Siberia, Russia

Pete Oxford / River in rainforest, Kaieteur Falls, Potaro River, Kaieteur National Park, Guyana

Pete Oxford / Potaro River cutting through Kaieteur Gorge, Kaieteur National Park, Guyana

Pete Oxford / Kaieteur Falls, Potaro River, Kaieteur National Park, Guyana

Pete Oxford / Kaieteur Falls where the Potaro River runs into the Essequibo River, Kaieteur National Park, Guyana

Pete Oxford / River in rainforest, Essequibo River, Rupununi, Guyana

Luis Quinta / Grass snake (Natrix natrix) swimming in river, Olo, Alvao, Portugal, June.

Niall Benvie / Bealach na Ba Pass, Wester Ross, Scotland, UK, November 2015.

Matthias Breiter / Trees in autumn along river, Sand River, Agawa Bay, Ontario, Canada

Yva Momatiuk & John Eastcott / Sockeye Salmon (Oncorhynchus nerka) group migrating upstream, Adams River, Roderick Haig-Brown Provincial Park, British Columbia, Canada

Loic Poidevin / Grizzly bear (Ursus arctos horribilis) mother watching cub catching salmon, Katmai National Park, Alaska, USA, August

Loic Poidevin / Grizzly bear (Ursus arctos horribilis) mother and cub in river, Katmai National Park, Alaska, USA, August

Loic Poidevin / Grizzly bear (Ursus arctos horribilis) cubs with salmon, Katmai National Park, Alaska, August. Small reproduction only.

Loic Poidevin / Grizzly bear (Ursus arctos horribilis) cubs with salmon, Katmai National Park, Alaska, August. Small reproduction only.

Andres M. Dominguez / European stonechat (Saxicola rubicola) male perched with mountainous habitat behind, Sierra de Grazalema Natural Park, southern Spain, February.

Andres M. Dominguez / Bacteria (Lepthotryx discophora) causing iridescent patterns and White willow tree leaf (Salix alba) in river, Sierra de Grazalema Natural Park, southern Spain, November.

Anup Shah / Eastern White-bearded Wildebeest (Connochaetes taurinus) herd crossing the Mara River. Masai Mara National Reserve, Kenya.

Anup Shah / Eastern White-bearded Wildebeest (Connochaetes taurinus) herd crossing the Mara River. Masai Mara National Reserve, Kenya.

Olga Kamenskaya / Pebbles reflected in the water surface at mouth of Sheryldy river, Lake Baikal, Siberia, Russia. September

Donald M. Jones / Elk (Cervus elaphus) bull and harem of females and calves along river, Athabasca River, western Canada

Hiroya Minakuchi / King Penguin (Aptenodytes patagonicus) colony, South Georgia Island

Hiroya Minakuchi / Amazon River Dolphin (Inia geoffrensis), Rio Negro, Brazil

Anup Shah / Blue Wildebeest (Connochaetes taurinus) herd crossing Mara River, Masai Mara, Kenya

Tim Fitzharris / Deciduous forest and river in fall, Little Buffalo River, Buffalo National River, Arkansas

Thomas Marent / Bonobo (Pan paniscus) walking through water, Lola Ya Bonobo Sanctuary, Democratic Republic of the Congo

Sean Crane / Polar Bear (Ursus maritimus) on ice, Seal River, Manitoba, Canada

Yva Momatiuk & John Eastcott / Sockeye Salmon (Oncorhynchus nerka) migrating upstream, Adams River, Roderick Haig-Brown Provincial Park, British Columbia, Canada

Richard Du Toit / African Elephant (Loxodonta africana) bulls drinking, Shingwedzi River, Kruger National Park, South Africa

Tim Fitzharris / West Indian Manatee (Trichechus manatus) mother and calf, Crystal River, Florida

David Tipling / 2020VISION / Alder flies (Sialis lutaria) hatching on River Wensum, Norfolk, England, UK, June

Anup Shah / Burchell's Zebra (Equus burchellii) and Blue Wildebeest (Connochaetes taurinus) herd crossing river, Mara River, Masai Mara, Kenya

Hiroya Minakuchi / Wattled Crane (Bugeranus carunculatus) flock flying, Okavango Delta, Botswana

Hiroya Minakuchi / Hippopotamus (Hippopotamus amphibius) calves, Okavango Delta, Botswana

David Noton / Dawn over the mountains and Nam Song River at Vang Vieng, Laos, March 2009.

Sean Crane / Polar Bear (Ursus maritimus) at sunrise, Hudson Bay, Seal River, Manitoba, Canada

Sean Crane / Lechwe (Kobus leche) running through water, Okavango Delta, Botswana

Markus Varesvuo / Dipper {Cinclus cinclus} at water, Finland

Gavin Hellier / Timelapse of traffic on the Nanpu Bridge spiral at night, Shanghai, China, 2011.