Gavin Hellier / Basilica of San Marco in San Marco Square, Venice, Italy

Alex Mustard / Stinker sponge (Ircinia felix) close up detail, growing on a coral reef, Georgetown, Grand Cayman, Cayman Islands, British West Indies, Caribbean Sea.

Franco Banfi / Spiny starfish (Marthasterias glacialis), Sponge (Sarcotragus foetidus) and Red gorgonian (Paramuricea clavata) colonising the crossbars of a sunken electricity pylon that fell into the sea during a s...

Franco Banfi / Red and yellow gorgonian (Paramuricea clavata) and Sponge (Sarcotragus foetidus) colonising the crossbars of a sunken electricity pylon that fell into the sea during a storm, Capri Island, Costa Amalf...

Sergio Hanquet / Black leather sponge (Sarcotragus spinosulus) on rock , Tenerife, Canary Islands.

Alex Mustard / Sponge spider crab / Decorator crab (Inachus sp) on Sea vases (Ciona intstinalis). Kinlochbervie, Sutherland, The Highlands, Scotland, United Kingdom. Loch Inchard, The Minch, North East Atlantic Ocea...

Alex Mustard / Sponge spider crab / Decorator crab (Inachus sp) clambers over Sea vases (Ciona intstinalis). Kinlochbervie, Sutherland, The Highlands, Scotland, United Kingdom. Loch Inchard, The Minch, North East At...

Franco Banfi / Black sponge (Ircinia muscarum) Punta Carena, Capri Island, Sorrentine Peninsula, Italy, Tyrrhenian Sea, Mediterranean.