Heike Odermatt / Walrus (Odobenus rosmarus), Hinlopen Strait, Svalbard, Norway

Heike Odermatt / Walrus (Odobenus rosmarus) on ice floe, Hinlopen Strait, Svalbard, Norway

Heike Odermatt / Walrus (Odobenus rosmarus) on ice floe, Hinlopen Strait, Svalbard, Norway

Heike Odermatt / Brunnich's Guillemot (Uria lomvia) nesting colony on cliff, Alkefjellet, Hinlopen Strait, Svalbard, Norway

Gary Bell/ Oceanwide / Veined Octopus (Octopus marginatus) hiding in glass jar, Lembeh Strait, Indonesia

Doug Gimesy / Little blue penguin (Eudyptula minor), two standing on rocks at night, silhouetted against Melbourne city lights. St Kilda breakwater, Victoria, Australia. December 2016. COP26 Countdown Photo Competi...

Doug Gimesy / Little penguin (Eudyptula minor) on rocks of St Kilda breakwater, Melbourne city lights in background. Victoria, Australia. January 2017.

Jordi Chias / Sponge (Mycale acerata) with diver. Lermaire strait, Antarctic Peninsula, Antarctica.

Tony Wu / North Pacific humpback whale (Megaptera novaeangliae kuzira) breaching, Icy Strait, Alaska, USA. July.

Alex Mustard / Orange painted frogfish (Antennarius pictus) fishing. Here the frogfish is illuminated by a snooted strobe and the background sand lit with a red LED torch. Bitung, North Sulawesi, Indonesia. Lembeh S...

Alex Mustard / Free swimming mimic octopus (Thaumoctopus mimicus). Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Free swimming mimic octopus (Thaumoctopus mimicus). Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Thorny seahorse (Hippocampus histrix) gripping onto a sponge. Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Pair of Western clown anemonefish (Amphiprion ocellaris) spawning orange eggs on the rock beneath their Magnificent sea anemone (Heteractis magnifica) home on a coral reef. This photo shows the larger...

Alex Mustard / Two female Common seahorses (Hippocampus kuda) fighting over territory on the seabed. The brief fight was preceeded by a ritualised, synchronised parade. Bitung, North Sulawesi, Indonesia. Lembeh Stra...

Alex Mustard / Common seahorse (Hippocampus kuda) female wrapping her prehensile tail around piece of wood on the seabed. Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Veined octopus (Amphioctopus marginatus) shelters inside an old clam shell, with silver-sides in the water above. Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Whitemargin stargazer (Uranoscopus sulphureus) sets an ambush in the sand at night. Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Veined octopus (Amphioctopus marginatus) emerging from its home in an old clam shell. Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Reef lizardifsh (Synodus variegatus) at a cleaning station, being cleaned by Holthuis anemone shrimps (Ancylomenes holthuisi). Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Shoal of three Bigfin reef squid (Sepioteuthis lessoniana) in open water at night. Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Portrait of a Giant frogfish (Antennarius commersoni) on a large Yellow elephant ear sponge (Ianthella basta). Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Forster's hawkfish (Paracirrhites forsteri) on a coral reef. Jackson Reef, Tiran, Sinai, Egypt. Strait of Tiran, Gulf of Aqaba, Egypt.

Georgette Douwma / Shortfin lionfish (Dendrochirus brachypterus). Lembeh Strait, North Sulawesi, Indonesia.

Georgette Douwma / Nudibranch (Chromodoris willani) with a scale worm. Lembeh Strait, North Sulawesi, Indonesia.

Georgette Douwma / Ribbon eel ( Rhinomuraena quaesita) Lembeh Strait, North Sulawesi, Indonesia.

Georgette Douwma / Colonial anemones (Amphianthus nitidus) with Green urn sea squirts (Didemnum molle) (Atriolum robustum). Lembeh Strait, North Sulawesi, Indonesia.

Georgette Douwma / Corkscrew or Long tentacle anemone (Macrodactyla doreensis). Lembeh Strait, North Sulawesi, Indonesia.

Georgette Douwma / Banggai cardinalfish (Pterapogon kauderni) with a Corkscrew or Long tentacle anemone (Macrodactyla doreensis). Lembeh Strait, North Sulawesi, Indonesia.

Georgette Douwma / Thornback cowfish (Lactoria fornasini). Lembeh Strait, North Sulawesi, Indonesia.

Georgette Douwma / Boxer Crab (Lybia tessellata) with sea anemones in its claws for defense. Lembeh Strait, North Sulawesi, Indonesia.

Georgette Douwma / Taylor's pygmy leatherjacket (Brachaluteres taylori). Lembeh Strait, North Sulawesi, Indonesia.

Terry Whittaker / Menai Strait and Telford suspension bridge. Isle of Anglesey, Wales, October 2018.

Alex Mustard / Tiger cardinalfish (Cheilodipterus macrodon) male mouth brooding a clutch of eggs behind his sharp teeth. Gubal Island, Egypt. Strait Of Gubal, Red Sea.

Alex Mustard / Veined octopus (Amphioctopus marginatus) sheltering in an old clam shell, with plankton swirling around it at night (captured as trails in the long exposure). Bitung, North Sulawesi, Indonesia. Lembeh...

Alex Mustard / Hawksbill turtle (Eretmochelys imbricata) male chomps on soft coral. Jackson Reef, Sinai, Egypt. Strait of Tiran, Red Sea.

Tony Wu / Humpback whales (Megaptera novaeangliae) bubble net feeding with mouths open at surface, example of cooperative hunting, Chatham Strait, Alaska, USA July

Alex Mustard / Red and black anemonefish (Amphiprion melanopus) in a Bulb tentacle sea anemone (Entacmaea quadricolor). Kri Island, Raja Ampat, West Papua, Indonesia, South East Asia. Dampier Strait, Tropical West P...

Matthias Breiter / Peaks rising above fog, Neva Strait, Sitka, Alaska

Alex Mustard / Portrait of a Severn's pygmy seahorse (Hippocampus severnsi) at Mioskon Island, Raja Ampat, West Papua, Indonesia. Dampier Strait. Tropical West Pacific Ocean.

Alex Mustard / Portrait of Bigfin squid (Sepioteuthis lessoniana) hovering in open water above a coral reef at night. Dampier Strait, Raja Ampat, West Papua, Indonesia. Tropical West Pacific Ocean

Constantinos Petrinos / Yellow stripe clingfish (Diademichthys lineatus) living in association with the Fire Urchin (Astropyga radiata) Lembeh Strait, North Sulawesi, Indonesia.

Constantinos Petrinos / Purple short tentacle mushroom coral (Fungia sp.) close up of polyps. Lembeh Strait, North Sulawesi, Indonesia.

Constantinos Petrinos / Bigfin reef squid (Sepioteuthis lessoniana) schooling parallel to one another. Lembeh Strait, North Sulawesi, Indonesia.

Constantinos Petrinos / Chromodorid nudibranch (Chromodoris annae) on Sea Squirt (Polycarpa aurata) Lembeh Strait, North Sulawesi, Indonesia.

Constantinos Petrinos / Peacock-tail anemone shrimp (Periclimenes brevicarpalis) living commensally with the Branching Sea Anemone (Actinodendron glomeratum). Lembeh Strait, North Sulawesi, Indonesia.

Alex Mustard / Eyes of Margined sole fish (Brachirus heterolapis) on its camouflaged body. Saonek Island, Raja Ampat, West Papua, Indonesia. Tropical West Pacific Ocean. Dampier Strait.

Alex Mustard / Reticulate stargazer (Uranoscopus sp.) emerging from the sand. Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Emperor shrimp (Periclimenes imperator / Zenopontonia rex) hitchhiking on large t-bar nudibranch (Ceratosoma trilobatum) The shrimp gains food source and protection on the toxic seaslug. Bitung, North...

Alex Mustard / Close up of tiny (10mm) Pygmy seahorse (Hippocampus bargibanti) living disguised in Muricella sp. sea fan. Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Portrait of Red Sea anemonefish (Amphiprion bicinctus) against open water. Abu Nuhas, Strait of Subal, Egypt. Gulf of Suez, Red Sea.

Alex Mustard / Shallow coral reef flat with corals (Pocillopora damicornis, Acropora humilis and Pocillopora verrucosa) in evening light. Gordon Reef, Strait of Tiran, Sinai, Egypt. Gulf of Aqaba, Red Sea.

Alex Mustard / Split level view of shallow coral reef in the Red Sea at sunset. Gordon Reef, Sinai, Egypt. Strait of Tiran, Gulf of Aqaba, Red Sea.

Cheryl-Samantha Owen / Johnstone strait coastline, East coast, Vancouver Island, British Columbia, Canada, July 2012.

Alex Mustard,Alex Mustard / Veined octopus (Amphioctopus marginatus) shelters in discarded coconut shell. Lembeh Strait, North Sulawesi, Indonesia. Molucca Sea.

Mark Carwardine / Pacific white-sided dolphin / Lag (Lagenorhynchus obliquidens) swimming fast, showing dorsal fin, Johnstone Strait, Vancouver Island, British Columbia, western Canada

Jeff Rotman / Wolf eel (Anarrichthys ocellatus) eating Red Sea Urchin (Strongylocentrotus franciscanus). Queen Charlotte Strait, British Columbia, Canada, North Pacific Ocean.

Jeff Rotman / Wolf eel (Anarrichthys ocellatus) eating Red Sea Urchin (Strongylocentrotus franciscanus). Queen Charlotte Strait, British Columbia, Canada, North Pacific Ocean.

Enrique Lopez-Tapia / Leopard seal (Hydrurga leptonyx) resting on iceberg, Gerlache Strait, Antarctic Peninsula, Antarctica, March 2010. WINNER OF NATURE CATEGORY OF POLLUX COMPEITITON / AWARDS 2013

Rick Tomlinson / Aerial view, taken from the mast, of SY "Adele"'s bow in the bay of an iceberg, Portal Point, Reclus Pennisula, Antarctica, January 2007 Non editorial uses must be cleared individually.

Roberto Rinaldi / John Dory fish (Zeus faber) on coral reef, Strait of Messina, Southern Italy

Roberto Rinaldi / Yellow fan coral / Seafan (Paramuricea clavata) amongst mass of invasive algae (Caulerpa taxifolia) with Rainbow wrasse fish (Coris julis), Strait of Messina, Southern Italy

Bryan and Cherry Alexander / Huge blocks of ice teeter, ready to become icebergs on the glaciated coast. Gerlache Strait, Southern Ocean, Antarctica, October 2009.

Juergen Freund / Whitemargin stargazer (Uranoscopus sulphureus) half hidden in the sand. Lembeh Strait, North Sulawesi, Indonesia

Juergen Freund / Eyed / Leopard sea cucumber (Bohadschia argus), close-up of the skin. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Coconut / Veined octopus (Octopus marginatus) hiding in its shell home. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Coconut / Veined octopus (Octopus marginatus) in a bottle cap getting a new shell to use as its home. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Coconut / Veined octopus (Octopus marginatus) hiding in its bottle cap home, using a shell as a door. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Coconut octopus / Veined octopus (Octopus marginatus) in its shell home. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Star shaped Pincushion / Pillow cushion starfish (Culcita novaeguinea), detail of the underbelly. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Coconut octopus / Veined octopus (Octopus marginatus) in its shell home. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Imperial / Emperor shrimp (Periclimenes imperator / Zenopontonia rex) on an Eyed / Leopard sea cucumber (Bohadschia argus). Lembeh Strait, North Sulawesi, Indonesia

Juergen Freund / Coconut octopus / Veined octopus (Octopus marginatus) in its shell home. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Coconut octopus / Veined octopus (Octopus marginatus) in its shell home. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Imperial / Emperor shrimp (Periclimenes imperator / Zenopontonia rex) on an Eyed / Leopard sea cucumber (Bohadschia argus). Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Star shaped Pincushion / Pillow cushion starfish (Culcita novaeguinea), detail of the underbelly. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Schooling Banggai cardinalfish (Pterapogon kauderni). Lembeh Strait, North Sulawesi, Indonesia

Juergen Freund / Imperial / Emperor shrimps (Periclimenes imperator / Zenopontonia rex) on a sea cucumber. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Carrier / Sea urchin crab (Dorippe frascone) carrying a fire urchin as a deterrent to predators. Lembeh Strait, North Sulawesi, Indonesia

Juergen Freund / Schooling Banggai cardinalfish in anemone tentacles. (Pterapogon kaudemi). Lembeh Strait, North Sulawesi, Indonesia

Juergen Freund / Ornate ghost pipefish (Solenostomus paradoxus), detail of the tail. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Coconut / Veined octopus (Octopus marginatus) hiding in its shell home. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Face of a Common lionfish (Pterios volitans) on top of the reef. Lembeh Strait, North Sulawesi, Indonesia

Juergen Freund / Baby orange Painted frogfish (Antennarius pictus) in a shell on the coral rubble. About 4mm in size. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Ornate ghost pipefish (Solenostomus paradoxus), close-up of the head. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Wonderpus (Wonderpus photogenicus) swimming well above the sea bed. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Two whip coral gobies (Bryaninops yongei) on a black coral sea whip. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Tropical blue-ringed octopus (Hapalochlaena lunulata) hunting. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Coconut / Veined octopus (Octopus marginatus) ready to flee from its coconut shell home. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Coconut / Veined octopus (Octopus marginatus) in its shell home. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Floating fruit of a Cannonball mangrove (Xylocarpus granatum) which when opened has seeds like a natural puzzle. Lembeh Strait, North Sulawesi, Indonesia, September 2009

Juergen Freund / Nudibranchs (Hypselodoris / Chromodoris bullocki) mating and laying eggs, Lembeh Strait, North Sulawesi, Indonesia

Juergen Freund / Poison ocellate octopus (Octopus mototi) on seabed. Lembeh Strait, North Sulawesi, Indonesia

Juergen Freund / Coconut / Veined octopus (Octopus marginatus) ready to flee from its coconut shell home. Lembeh Strait, North Sulawesi, Indonesia.

Alex Mustard / In-camera motion blur image of a female Hedgehog Seahorse (Hippocampus spinosissimus). Lembeh Strait, Sulawesi, Indonesia, Molluca Sea, March.