Paul D Stewart / Aerial view of Grand Prismatic thermal spring in Yellowstone National Park, USA. The bright colours are natural, coming from thermophile bacteria in the water. People can be seen walking on the raised...

Linda Pitkin / 2020VISION / Dead man's fingers (Alcyonium digitatum), growing on rock faces below the kelp, St Abbs (St Abbs and Eyemouth Voluntary Marine Reserve), Berwickshire, Scotland, UK, October 2011. Did you know? Soft co...

Benoit Stichelbaut / Workers cleaning beach of spilt oil from cargo boat "TK Bremen", beached by heavy winds. Erdeven, Brittany, France, December 16th 2011.

Aflo / N-14405 Double waterfall in woodland, Tochigi, Japan.

Georgette Douwma / Burrowing sea cucumber (Neothyonidium magnum). The massive tentacular crown is the only part that is visible, the rest is buried in the sand. Feeds by picking particles out of the water with the tenta...

Niall Benvie / A glass of clean water.

David Woodfall / Detail of slate and metamorphic rocks in bed of river Marteg, upland SSSI River, the best example of clean upland river in Wales, Gilfach Nature Reserve, Radnorshire Wildlife Trust, Powys, Wales, UK M...

David Pattyn / European flamingo (Phoenicopterus roseus) bathing, at height of courtship season they clean their plumage a lot, Camargue, France, April

David Pattyn / European flamingo (Phoenicopterus roseus) bathing, at height of courtship season they clean their plumage a lot, Camargue, France, April

Roy Mangersnes / Water polluted by mercury from gold mining processes joins clean water of the Mapiri River, part of the upper reaches of the Amazon, Bolivia, November

Juergen Freund / Spectacled flying foxes (Pteropus conspicillatus) inside cage with volunteer Andrew providing clean water, Tolga Bat Hospital, Atherton, North Queensland, Australia. January 2008.

Suzi Eszterhas / Polluted murky water of main river meeting clean black water of Sekonyer River, Tanjung Puting National Park, Indonesia