Gary Bell/ Oceanwide / Red tide, Heron Island, Great Barrier Reef, Queensland, Australia

Chris Gomersall / Large flock of Red knot (Calidris canutus) moving at high tide roost, in winter plumage, Snettisham RSPB Reserve, Norfolk, England, UK, September.

John Waters / Large mixed flock of Knot (Calidris canutrus), Dunlin (Calidris alpina) and Golden plover (Pluvialis apricaria) in flight at high tide, Steart Marshes WWT Reserve, Somerset, England, UK, December.

Tom Gilks / Zanzibari woman at low tide with harvested seaweed (eucheuma spinosum) Matemwe, Zanzibar, Tanzania

Danny Green / Knot (Calidris canutus) and grey plover (Pluvialis squatarola) roost at high tide with numerous birds packed tightly together, Snettisham, Norfolk, October. Bookplate from Danny Green's 'The Long Jour...

Nick Upton / Split level view of a Beadlet anemone (Actinia equina) attached to a boulder encrusted with Maerl (Lithothamnion glaciale) a red coralline alga, in a large rockpool, Crail, Scotland, UK, July

Matthew Maran / Surfer Benj Yougson at Long Beach. Pacific Rim National Park Reserve, west coast of Vancouver Island, Canada, September 2010. Model released

Floris van Breugel / Giant Red Sea Urchins (Strongylocentrotus franciscanus) Purple sea urchins (Strongylocentrotus purpuratus) and Sea Anenomes (Anthopleura) underwater, in tide pools along Californian coastline, USA.

Luiz Claudio Marigo / Red mangrove (Rhizophora mangle) roots exposed at low tide, eastern coast of Ceara¡ State, near Camocim town, Northeastern Brazil.

David Tipling / Mixed flock of Knot {Calidris canutus} and Oystercatcher {Haematopus ostralegus} at high tide roost, Snettisham RSPB Reserve, The Wash, Norfolk,UK, summer

David Tipling / Large flock of Knot {Calidris canutus} at high tide roost, Snettisham RSPB Reserve, The Wash, Norfolk, UK, August

Juergen Freund / Casts of 130 million year old dinosaur footprints (the original footprints are only exposed at low tide) at Gantheaume Point, with its distinctive red soils. Broome, Western Australia.