Shane Gross / Bubble coral shrimp (Vir philippinensis) on Bubble coral (Plerogyra sp). Anilao, Philippines.

David Fleetham / Bubble coral shrimp (Vir philippinensis) on Bubble coral (Plerogyra sp), Philippines.

Pascal Kobeh / Divers are setting up concrete reef balls to build an artificial reef, Philippines, Sulu Sea. August 2014.

Alex Mustard / Diver blowing bubble rings, while resting on the sand, East End, Grand Cayman, Cayman Islands, British West Indies, Caribbean Sea, January 2011.

Jeff Rotman / Free diver coming up from dive to explore coral reef, Sinai, Egypt, Red Sea Model released Model released.

Pascal Kobeh / Bubble-coral (Plerogyra sp.) New Caledonia, Pacific Ocean.

Pascal Kobeh / Coleman's bubble coral shrimp (Vir colemani) with its eggs in a bubble-coral (Plerogyra sinuoasa) where it is protected, New Caledonia, Pacific Ocean Completed Review

Gary Bell/ Oceanwide / Hard Tube Coco Worm (Protula magnifica) filter feeding in Euphyllia Coral (Euphyllia ancora), Great Barrier Reef, Australia

Georgette Douwma / Kaleidoscopic image of Bubble tip anemone (Entacmaea quadricolor). Raja Ampat, West Papua, Indonesia.

Georgette Douwma / Kaleidoscopic image of Bubble tip anemone (Entacmaea quadricolor). Raja Ampat, West Papua, Indonesia.

David Fleetham / Orang utan crab (Achaeus japonicus), with its red algae growth, on bubble coral, Philippines.

Franco Banfi / Rounded bubblegum / Bubble coral (Plerogyra sinuosa) with two Gobies (Gobiidae) on it, Lazi Pier, Dumaguete, East Negros Island, Central Visayas, Philippines, Pacific Ocean.

Constantinos Petrinos / Acoel flatworms (Waminoa sp.) on Bubble Coral (Plerogyra sinuosa) Lembeh Strait, North Sulawesi, Indonesia.

Linda Pitkin / Banggai Cardinalfish (Pterapogon kauderni), sheltering against Bubble Coral (Plerogyra sinuosa) Lembeh Strait, North Sulawesi, Indonesia, February 2016

Georgette Douwma / Acoel flatworms (Waminoa sp) on polyps of Bubble coral (Plerogyra sinuosa) Indonesia. This flatworm can cover the whole surface of some corals, leaving them no way to catch plankton and their symbioti...

Georgette Douwma / Acoel flatworms (Waminoa sp) on polyps of Bubble coral (Plerogyra sinuosa) Indonesia. This flatworm can cover the whole surface of some corals, leaving them no way to catch plankton and their symbioti...

Norbert Wu / Euphyllia Coral (Euphyllia ancora) with polyps extended, Ambon, Indonesia

Georgette Douwma / Lined butterflyfish (Chaetodon lineolatus), pair feeding on Bubble coral (Plerogyra sinuosa). Egypt, Red Sea.

Juergen Freund / Bubble snail (Hydatina physis) on white background, Batanagas, Philippines.

Juergen Freund / Bubble snail (Hydatina physis) Batangas, Philippines.

Juergen Freund / Head-shielded slug (Philinopsis cyanea) Batangas, Philippines

Juergen Freund / Algae sailor's eyeball / Bubble algae (Valonia ventricosa) Kimbe Bay, West New Britain, Papua New Guinea.

Juergen Freund / Bubble coral (Plerogyra sinuosa) with parasitic flatworms (Waminoa sp). Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Orangutan crab (Achaeus japonicus) on bubble coral. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Bubble coral (Plerogyra sinuosa) on the reef. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Orangutan crab (Achaeus japonicus) in bubble coral (Plerogyra sinuosa) Kimbe Bay, Papua New Guinea, Indo-Pacific.

Chris Newbert / Bubble Coral (Cynarina sp) detail, Indonesia

Chris Newbert / Bubble Coral (Plerogyra simplex), Indonesia

GEORGETTE DOUWMA / Spinecheek anemonefish (Premnas biaculeatus) amongst tentacles of its exclusive host, the Bubble tip anemone (Entacmaea quadricolor) Raja Ampat, West Papua, Indonesia.

GEORGETTE DOUWMA / Spinecheek anemonefish (Premnas biaculeatus) amongst tentacles of its exclusive host, the Bubble tip anemone (Entacmaea quadricolor) Raja Ampat, West Papua, Indonesia.

GEORGETTE DOUWMA / Dusky / Red and black anemonefish (Amphiprion melanopus) amongst tentacles of Bubble tip anemone (Entacmaea quadricolor) Raja Ampat, West Papua, Indonesia.

Juergen Freund / Bubble coral shrimps (Vir philippinensis) on bubble coral, Irian Jaya / West Papua, Indonesia (West Papua).

Constantinos Petrinos / Bubble or grape coral (Plerogyra sinuosa) Sulawesi, Indonesia

Juergen Freund / Bubble coral with tentacles extended at night {Physogyra lichtensteini} Indo-Pacific

Birgitte Wilms / Hard Coral (Euphyllia paraencora) polyps, 60 feet deep, Solomon Islands

Chris Newbert / Rounded Bubblegum Coral (Plerogyra sinuosa), Coral Sea

Fred Bavendam / Yellowfin Goatfish (Mulloides vanicolensis) school near coral reef observed by scuba diver, often gather in large schools during the day and disperse at night to feed, Great Barrier Reef, Queensland,...

Norbert Wu / Euphyllia Coral (Euphyllia ancora) a type of stony coral with distinctive polyps, Papua New Guinea

Fred Bavendam / Coral Shrimp (Vir philippinensis) living on Rounded Bubblegum Coral (Plerogyra sinuosa) green spots are Acoelous Flatworms, Manado, North Sulawesi, Indonesia

Norbert Wu / Coral Shrimp (Vir philippinensis) gain protection among stinging tentacles of Bulb Tentacle Sea Anemone (Entacmaea quadricolor) filled with eggs, Philippines

David Hall / Parrotfish sleeping in mucous bubble at night (Scarus festivus) Indonesia. The bubble prevents predators from smelling the fish while it sleeps.

Jeff Rotman / Pearl bubble coral polyps {Physogyra lichtensteini} Red Sea

Juergen Freund / Coral goby {Pleurosicya mossambica} on bubble coral Philippines

Gary Bell/ Oceanwide / Coral Shrimp (Vir philippinensis) on Rounded Bubblegum Coral (Plerogyra sinuosa), Anilao, Philippines

Gary Bell/ Oceanwide / Coral Shrimp (Vir philippinensis) on Rounded Bubblegum Coral (Plerogyra sinuosa), Anilao, Philippines

Gary Bell/ Oceanwide / Euphyllia Coral (Euphyllia ancora) polyps, Great Barrier Reef, Australia

Gary Bell/ Oceanwide / Rounded Bubblegum Coral (Plerogyra sinuosa), Great Barrier Reef, Australia

David Fleetham / Bubble coral shrimp (Vir philippinensis) on Bubble coral (Plerogyra sinuosa). The brown oval objects are acoel flatworms (Waminoa sp.), Mabul Island, Malaysia.

David Fleetham / Two Commensal shrimp (Vir philippinensis) on Bubble Coral (Plerogyra sinuosa), Indonesia. The greenish brown circular markings are flatworms (Waminoa sp.)

Pete Oxford / Rounded Bubblegum Coral (Plerogyra sinuosa), Raja Ampat Islands, Indonesia

Roberto Rinaldi / Commensal shrimp / Anemone shrimp (Pliopontonia sp) on a bubble coral (Plerogyra sp), Lankayan Island, Borneo

Roberto Rinaldi / Bubble coral (Euphyllia sp), Farasan Islands, Saudi Arabia.

Juergen Freund / Anemone shrimp {Thor amboinensis} on bubble coral, Indo pacific

Constantinos Petrinos / Bubble coral shrimp {Vir philippinensis} on Bubble coral {Plerogyra sinuosa} Sulawesi, Indonesia

Flip Nicklin / Inuit Andrew Taqtu investigates seastars, corals and anemones, Arctic

Chris Newbert / Euphyllia Coral (Euphyllia ancora) close-up of polyps, Coral Sea

Juergen Freund / Flatworms on Bubble coral {Platyhelminthes, Waminoa species} Indo Pacific

David Fleetham / Purple fairy basslets (Pseudanthias tuka) schooling around hard coral reef with scuba diver in background, Philippines, Pacific Ocean. Model released.

David Fleetham / A dive instructor hand signalling to student diver over a reef, Molokini Islet. off Maui, Hawaii, Pacific Ocean. Model released.

David Fleetham / Three scuba divers swimming over coral reef looking at Slate pencil sea urchins (Heterocentrotus mammillatus), Molokini Marine Preserve, Maui, Hawaii, Pacific Ocean. Model released.

David Fleetham / Split-shot of coral reef below water and Two Tree Island above, Kadavu Island, Fiji, Pacific Ocean. November, 2012.

David Fleetham / Mozambique ghost goby (Pleurosicya mossambic) resting on on Bubble coral, (Physogyra lichtensteini), Philippines, Pacific Ocean.

David Fleetham / A large Barrel sponge (Xestospongia testudinaria), which filters organic material from the water column, on a coral reef with a scuba diver in the background, Bali, Indonesia, Indo-Pacific. Model rele...

David Fleetham / Two Cymbal bubble snails (Haminoea cymbalum) side by side on a reef, Fiji, Pacific Ocean

Magnus Lundgren / Bubble coral shimp (Vir philippinensis) full of eggs, resting in Bubble coral (Plerogyra sinuosa), Triton Bay, West Papua, Indonesia, Pacific Ocean.

David Fleetham / Bubble coral (Plerogyra sinuosa) on acoral reef, the Philippines.

David Fleetham / Bleeker's Parrotfish (Chlorurus bleekeri), surrounded by mucus bubble, on sea bed in reef at night, South Pacific, Fiji.

Pascal Kobeh / A friendly Atlantic goliath grouper or Giant seabass (Epinephelus itajara) with a scuba diver reaching out to touch it, The Gardens of the Queen, Cuba, Caribbean Sea. Model released.

Alex Mustard / Detail of the expanded polyps of Bubble coral (Plerogyra sp.) on a reef. Baa Atoll, Maldives. Indian Ocean

David Fleetham / Neon dwarfgoby (Eviota atriventris) on Bubble coral (Plerogyra sinuosa) Philippines.

David Fleetham / Three cymbal bubble snails (Haminoea cymbalum) gathered together in a ball on a reef, Fiji.

Georgette Douwma / Translucent coral goby (Bryaninops erythrops) resting on Bubble coral (Plerogyra sinuosa). Derawan Islands, East Kalimantan, Indonesia.

Georgette Douwma / Acoel flatworm (Waminoa sp) group on Bubble coral (Plerogyra sp). Derawan Islands, East Kalimantan, Indonesia.

Georgette Douwma / Orangutan crab (Oncinopus sp) resting on Bubble coral (Plerogyra sinuosa). Derawan Islands, East Kalimantan, Indonesia.

Linda Pitkin / Bubble coral shrimp (Vir philippinesis) in symbiotic commensal relationship with Bubble coral (Plerogyra sinuosa). Lembeh Strait, North Sulawesi, Indonesia.