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

Juergen Freund / Timelapse of Giant sea cucumbers (Thelenota ananas) moving underwater, with a Giant clam (Tridacna gigas) in the background, Great Barrier Reef, Queensland, Australia, 2015.

David Fleetham / Opening in the mantle of Giant clam (Tridacna gigas) Tubbataha Reef, Philippines.

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...

Juergen Freund / Giant clam (Tridacna gigas) Raja Ampat, West Papua, Indonesia.

Pascal Kobeh / Giant clam (Tridacna) on 'Lotus' artificial reef, built in 2001 with a steel frame using mild electric currents to encourage coral growth, with diver in the background. Vabbinfaru Island in North Male...

Juergen Freund / Sea squirts / ascidians / tunicates on a clam, Indo-pacific

Juergen Freund / Anthea Melsen smiles shyly as she comes out of the water after looking at her grandfather's coral and clam gardens, Onma Lodge, Kolombangara, Western Province, Solomon Islands, July 2010

Doug Perrine / Giant clam {Tridacna sp} Palau, Micronesia

Michael Pitts / Giant clam mantle {Tridacna gigas} and siphon, Palau, Micronesia

Constantinos Petrinos / Giant clam {Tridacna gigas} biggest bivalve species in world, Sulawesi Indonesia. Hermaphrodite producing both eggs and sperm