David Fleetham / Hawksbill Turtle (Eretmochelys imbricata) and a shoal of fish near sea surface. Tubbataha Reef, Philippines.

Danny Green / Polar bear (Ursus maritimus) walking across sea ice, reflected in water. Svalbard, Norway, July.

Alex Mustard / Spinner dolphin (Stenella longirostris) pod socialising close to surface. Fury Shoal, Sataya Reef, Marsa Alam, Egypt.

Alex Mustard / Oceanic whitetip shark (Carcharhinus longimanus) swimming close to surface. Brothers Islands, Egypt.

Tony Wu / Humpback whale (Megaptera novaeangliae australis) male calf playing at ocean surface after coming up to breathe. Vava'u Islands, Tonga.

Alex Mustard / Commensal emperor shrimp (Periclimenes imperator) moves across the colourful red patterned surface of its host Candycane sea cucumber (Thelenota rubralineata). Misool, Raja Ampat, West Papua, Indonesi...

Alex Mustard / Killer whales (Orcinus orca) at the surface in an Arctic fjord in Spildra, northern Norway, with sea birds. Arctic Ocean

Alex Mustard / Blue whale (Balaenoptera musculus) swims beneath the surface of the ocean. Indian Ocean, off Sri Lanka.

Alex Mustard / Pod of False killer whales (Pseudorca crassidens) swimming beneath the surface of the ocean. Indian Ocean, off Sri Lanka.

Alex Mustard / Green turtle (Chelonia mydas) descending after breathing at the surface. Misool, Raja Ampat, West Papua, Indonesia. Ceram Sea. Tropical West Pacific Ocean.

Doc White / Sea Otter, (Enhydra lutris), young male, Elkhorn Slough, California, USA. January

Nick Hawkins / Steller's sea lions (Eumetopias jubatus) off the coast of the Great Bear Rainforest, near Bella Bella, British Columbia, Canada. August