Alex Mustard / Double exposure of a Tompot blenny (Parablennius gattorugine) with underwater sun beams. Swanage, Dorset, England, United Kingdom.

Tony Wu / Crab-eye goby (Signigobius biocellatus), mimics crab with eye-spot markings on dorsal fins and back and forth movement. Loloata Island, Papua New Guinea.

Alex Mustard / Saddleback anemonefish (Amphiprion polymnus) barks a warning as it guards a clutch of developing eggs (beneath it) laid on a small stone, below a fold in its home, a Haddon's sea anemone (Stichoda...

Alex Mustard / Giant hogfish (Bodianus macrognathos) male yawning at a cleaning station run by juvenile Spanish hogfish (Bodianus rufus). Jardines de la Reina, Gardens of the Queen National Park, Cuba. Caribbean Sea...

Philippe Clement / Female Common kingfisher (Alcedo atthis) diving and catching a Nine-spined stickleback (Pungitius pungitius) fish, stuns and eats it, Belgium, June.

Tony Wu / Male Korean seahorse (Hippocampus haema) giving birth. Kumamoto Prefecture, Kyushu, Japan.

Brandon Cole / Crescent-tail bigeyes (Priacanthus hamrur), and Grey reef sharks (Carcharhinus amblyrhynchos). French Polynesia, Pacific Ocean.

Brandon Cole / Crocodile fish (Cymbacephalus beauforti) camouflaged, Egypt, Red Sea.

Brandon Cole / Masked butterflyfish (Chaetodon semilarvatus) Egypt, Red Sea.

Brandon Cole / Oceanic whitetip shark (Carcharhinus longimanus) and Pilotfish (Naucrates ductor) swimming under a stormy surface. Egypt, Red Sea.

Brandon Cole / Giant moray eel (Gymnothorax javanicus), peering up from inside colony of Plate Fire Coral (Millepora platyphylla). Egypt, Red Sea.

Brandon Cole / Yellowfin tuna (Thunnus albacores) Baja, Mexico, Pacific Ocean.

Brandon Cole / Steel pompano (Trachinotus stilbe) fish swimming under stormy seas at Roca Redonda offshore Baja, Mexico, Pacific Ocean.

Brandon Cole / Piraputanga (Brycon hilarii) fish swimming in clear river with trees visible overhead. Brazil, South America.

Franco Banfi / Conger eel, (Conger conger) on Teti shipwreck which sank on a stormy night on 23 May 1930, Komiza, Vis Island, Croatia, Adriatic Sea. .

Doug Perrine / Yellowfin tuna (Thunnus albacares) and Pantropical spotted dolphins (Stenella attenuata) feeding on bait fish, Pacific Ocean off southern Costa Rica.

Sergio Hanquet / Wide-eyed flounder (Bothus podas) portrait showing eyes above head, Tenerife, Canary Islands.

Sergio Hanquet / Pilot whale (Globicephala macorhynchus) close-up of submerged adult. Tenerife, Canary Islands.

Sergio Hanquet / Yellowfin tuna (Thunnus albacares) hunting mackerel (Scomber colias) Tenerife, Canary Islands.

Claudio Contreras / Foureye butterflyfish (Chaetodon capistratus) couple feeding on coral, Guanahacabibes Peninsula National Park, Pinar del Rio Province, western Cuba.

Claudio Contreras / Black grouper (Mycteroperca bonaci), and Caribbean Reef Shark (Carcharhinus perezi), Jardines de la Reina / Gardens of the Queen National Park, Caribbean Sea, Ciego de Avila, Cuba.

Claudio Contreras / Black grouper (Mycteroperca bonaci), and Caribbean Reef Shark (Carcharhinus perezi), Jardines de la Reina / Gardens of the Queen National Park, Caribbean Sea, Ciego de Avila, Cuba.

Nick Hawkins / Atlantic sturgeon (Acipenser sturio), Minas Basin of the Bay of Fundy, Canada. July 2019.

Nick Hawkins / Common shiners (Luxilus cornutus) school below lilly pads in lake, Nova Scotia, Canada. July.

David Hall / Split level of a Sockeye salmon (Oncorhynchus nerka) in shallow water; Adams River, British Columbia, Canada. October.

David Hall / Split level of Sockeye salmon (Oncorhynchus nerka) during migration; Adams River, British Columbia, Canada. October.

David Hall / Sockeye salmon (Oncorhynchus nerka) migration, Adams River, British Columbia, Canada. October.

David Hall / Sockeye salmon (Oncorhynchus nerka) migration, Adams River, British Columbia, Canada. October.

Shane Gross / Panamic Cushion Sea Star (Pentaceraster cumingi) and a school of Yellow-tailed Grunt (Anisotremus interruptus), Galapagos Island, Ecuador. December.

Shane Gross / Red mangrove (Rhizophora mangle) habitat with shoal of Silversides (Atherinomorus lacunosus), Eleuthera, Bahamas. August.

Shane Gross / Flying fish (Exocoetidae) caught and drowned in a drift net off the coast of Sri Lanka.

Franco Banfi / Tiger moray / Fangtooth Moray (Enchelycore anatina), South Tenerife, Canary Islands, Atlantic Ocean.

Franco Banfi / Tiger moray / Fangtooth Moray (Enchelycore anatina) and Black moray eel (Muraena augusti), South Tenerife, Canary Islands, Atlantic Ocean.

Franco Banfi / Blue shark (Prionace glauca) and Pilot fish (Naucrates ductor), Pico Island, Azores, Portugal, Atlantic Ocean

Franco Banfi / Blue shark (Prionace glauca) with fishing hook caught in mouth and Pilot fish (Naucrates ductor), Pico Island, Azores, Portugal, Atlantic Ocean

Franco Banfi / Short-finned pilot whale (Globicephala macrorhynchus) female carrying dead calf, South Tenerife, Canary Islands, Atlantic Ocean. Runner-up in Underwater Worlds category of MontPhoto competition 2020.

Franco Banfi / Short-finned pilot whale (Globicephala macrorhynchus) dorsal fin surfacing. South Tenerife, Canary Islands, Atlantic Ocean

Franco Banfi / Cuckoo wrasse (Labrus mixtus) male in front of Red sea fan, (Paramuricea clavata), Stupiste In dive site, Vis Island, Croatia, Adriatic Sea, Mediterranean

Alex Mustard / Long exposure of a group of Tarpon (Megalops atlanticus) hunt Silversides (Atherinidae) inside a coral cavern. George Town, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea.

Alex Mustard / Dugong (Dugong dugon) male, swims over seagrass meadow (Halophila stipulacea) accompanied by a young Golden trevally (Gnathanodon speciosus). Marsa Nabaa, Marsa Alam, Egypt. Red Sea

Alex Mustard / Dugong (Dugong dugon) male feeding on a seagrass meadow (Halophila stipulacea), accompanied by a young Golden trevally (Gnathanodon speciosus). Marsa Nabaa, Marsa Alam, Egypt. Red Sea

Alex Mustard / Dugong (Dugong dugon) male feeding on a seagrass meadow (Halophila stipulacea), accompanied by a young Golden trevally (Gnathanodon speciosus). Marsa Nabaa, Marsa Alam, Egypt. Red Sea

Ismaele Tortella / Underwater shot of Killer whales (Orcinus orca) hunting Atlantic herring (Clupea harengus), northern Norway, November.

Ismaele Tortella / Underwater shot of Killer whales (Orcinus orca) hunting Atlantic herring (Clupea harengus), northern Norway, November.

Shane Gross / Pink anemonefish (Amphiprion perideraion) living in symbiotic association with Magnificent sea anemone (Heteractis magnifica) Palau.

Shane Gross / Pink anemonefish (Amphiprion perideraion) living in symbiotic association with Magnificent sea anemone (Heteractis magnifica), Palau

Shane Gross / Red lionfish (Pterois volitans) swimming under a coral ledge, Palau.

Shane Gross / Clark's Anemonefish (Amphiprion clarkii) tending to her eggs. Kimbe Bay, Papua New Guinea