Alex Mustard / Hawksbill turtle (Eretmochelys imbricata) pair circling each other above coral reef. Seven Mile Beach, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea.

Tui De Roy / King Penguin (Aptenodytes patagonicus) group on beach, Volunteer Beach, East Falkland Island, Falkland Islands

Sue Daly / Close-up of a Seven rayed starfish (Luidia ciliaris) moving over the seabed, showing use of its tube feet to walk, Sark, British Channel Islands, UK, August.

Sue Daly / Seven rayed starfish (Luidia ciliaris) moving over the seabed, showing use of its tube feet to walk, Sark, British Channel Islands, UK, August.

Gavin Hellier / Anakena beach, monolithic giant stone Moai statues of Ahu Nau Nau, four of which have topknots, Isla de Pascua / Easter Island, Rapa Nui, Chile 2008

Alex Mustard / Planktonic sea walnut ctenophore (Mnemiopsis mccradyi) in open water, Seven Mile Beach, Grand Cayman, Cayman Islands, British West Indies, Caribbean Sea.

Alex Mustard / A split level view of shallow water and clouds in summer, Seven Mile Beach, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea.

Andy Rouse / Landscape of Seven Islands and arctic coastline. Svalbard, Norway, May 2010.

Andy Rouse / Polar bear footprints on beach, Seven Islands, Svalbard, Norway

Gerry Ellis / Conch shell on Seven Mile Beach, Grand Turk Island, Turk and Caicos Islands, Caribbean

Nick Garbutt / King penguin (Aptenodytes patagonicus) group of seven walking one behind the other along sand bar. St Andrews Bay, South Georgia. November.

Alex Mustard / Box ray (Mobula tarapacana) swimming above USS Kittiwake shipwreck. Seven Mile Beach, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea.