Sergio Hanquet / Green sea turtle (Chelonia mydas), two viewed from above. Tenerife, Canary Islands.

Philippe Clement / Lined top shells (Phorcus lineatus) in a rock pool, Normandy, France, June

Philippe Clement / Lined top shells (Phorcus lineatus) and Common european limpets (Patella vulgata) in a rock pool, Normandy, France, June.

Sandra Bartocha / Sea shells in sand, North sea, Germany, September

Juergen Freund / Green turtle (Chelonia mydas) swimming through the sea near a coral reef, seen from above. Sipadan Island, Semporna, Sabah, Malaysia, June

Alex Mustard / A young California sealion (Zalophus californianus) playing with a starfish, inside an underwater cave. The pups will pick up a variety of objects (such as starfish, lumps of coral, shells and feather...

Alex Mustard / A young California sealion (Zalophus californianus) playing with a starfish, inside an underwater cave. The pups will pick up a variety of objects (such as starfish, lumps of coral, shells and feather...

Sue Daly / Hawksbill turtle (Eretmochelys imbricata) with algal growth on carapace, Cebu, Philippines, March, Endangered species

Wild Wonders of Europe / Novák / Sand and shells, Japsand, Schleswig-Holstein Wadden Sea National Park, Germany, April 2009

Wild Wonders of Europe / Lundgren / Kelp with Common / Red sunstar (Crossaster papposus) and shells, Moere coastline, Norway, February 2009

Juergen Freund / X-ray of shell of the Venus Comb Murex {Murex pecten}

Juergen Freund / X-ray of shell of spider conch {Lambis chiragra}