Alex Mustard / Yellow tube sponge (Aplysina fistularis) on coral reef, diver exploring in background. Black Rock Drop Off, East End, Grand Cayman, Cayman Islands, British West Indies. Model released.

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

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 / Yellow tube sponge (Aplysina fistularis) on a coral reef, with the camera rotated during the long exposure. East End, Grand Cayman, Cayman Islands. British West Indies. Caribbean Sea.

Alex Mustard / Spotlight goby (Gobiosoma louisae) looking out from inside a Yellow tube sponge (Aplysina fistularis), growing on a coral reef. Bloody Bay Wall, Little Cayman, Cayman Islands, British West Indies. Car...

Olga Kamenskaya / Endemic freshwater sponge (Lubomirskia baicalensis), Lake Baikal, Siberia, Russia. October.

Olga Kamenskaya / Endemic sponge (Lubomirskia baicalensis), Lake Baikal, Siberia, Russia. September 2013

Franco Banfi / Orange elephant ear sponge (Agelas clathrodes) Santa Lucia, Camaguey, Cuba, Caribbean Sea, Atlantic Ocean

Claudio Contreras / Giant barrel sponge (Xestospongia muta) Cozumel Reefs National Park, Cozumel Island, Caribbean Sea, Mexico, February

Alex Mustard / Yellow tube sponges (Aplysina fistularis) growing on a Caribbean coral reef. Cayman Brac, Cayman Islands. Caribbean Sea.

Georgette Douwma / Erect rope sponge (Amphimedon compressa) Bonaire, Netherlands Antilles, Caribbean, Atlantic Ocean.

Georgette Douwma / Stove-pipe sponge (Aplysina archeri) Bonaire, Netherlands Antilles, Caribbean, Atlantic Ocean.