Pascal Kobeh / Giant clam (Tridacna) on 'Lotus' artificial reef, built in 2001 with a steel frame using mild electric currents to encourage coral growth, with diver in the background. Vabbinfaru Island in North Male...

Alex Mustard / Vibrant Red Sea reef scene, with orange female Scalefin anthias (Pseudanthias squamipinnis) swarming in front of Fire coral (Millepora dichotoma) feeding on plankton brought to the reef by currents. R...

Linda Pitkin / 2020VISION / Water-crowfoot (Ranunculus fluitans subsp. penicillatus) flowering underwater, Cumbria, England, UK, September. Did you know? The latin name for this genus 'Ranunculus' comes from the Latin for 'Litte...

Graham Eaton / Underwater landscape within a mountain stream, showing water turbulence, Snowdonia NP, Gwynedd, Wales, UK, December

Graham Eaton / A split-level image of a mountain stream, in autumn, with water droplets on lens, Nant Ffrancon Valley, Snowdonia NP, Gwynedd, Wales, UK, October

Graham Eaton / Underwater view of a rapidly flowing mountain stream, Snowdonia NP, Gwynedd, Wales, UK, November

Christophe Courteau / Timber washed onto the shore by the strong arctic currents. There are no trees on Spitzbergen, all the wood comes from the Siberian Coast, Poolepynten, Spitzbergen, Svalbard, Norway, July 2011

Jerry Monkman / A kayaker plays in a hole in Tariffville Gorge on the Farmington River in Tariffville, Connecticut. Class III whitewater. May 2007. Model released.

Wild Wonders of Europe / Ruiz / Krinice River flowing past rock faces almost at right angles, Dlouhy Dul, Ceske Svycarsko / Bohemian Switzerland National Park, Czech Republic, September 2008

Wild Wonders of Europe / Ruiz / Krinice River flowing past rock faces, Dlouhy Dul, Ceske Svycarsko / Bohemian Switzerland National Park, Czech Republic, September 2008

Wild Wonders of Europe / Lundgren / Whirlpool in the sea, Saltstraumen, Bod, Norway, October 2008

Wild Wonders of Europe / Lundgren / The fastest current / Maelstrom in the world, Salstraumen, Bod, Norway, October 2008