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

Alex Mustard / Portrait of Blacktip grouper (Epinephelus fasciatus) resting in Barrel sponge (Xestospongia testudinaria) Mabul Island, Sabah, Borneo, Malaysia. Sulawesi Sea.

Georgette Douwma / Barrel Sponge (Xestospongia testudinaria) on coral reef with soft corals (Scleronephthya sp), gorgonian and Lyretail anthias (Pseudanthias squamipinnis). Komodo National Park, Indonesia.

Juergen Freund / Massive barrel sponge (Xestospongia testudinaria) and diver. Tubbataha Reef National Marine Park, Palawan, Philippines, April 2009. Model released.

Juergen Freund / Giant barrel sponge (Xestospongia testudinaria) studded with crinoids / featherstars with diver in the background, Kimbe Bay, West New Britain, Papua New Guinea.

Michele Westmorland / Diver at healthy reef system with large Barrel sponge (Xestospongia testudinaria) covered with crinoids / feather stars (Oxycomanthus bennetti). Mulloway's Reef, Tufi, Papua New Guinea, model released...

Fred Bavendam / Giant Barrel Sponge (Xestospongia testudinaria) spawning, Bali, Indonesia

Jeff Rotman / Diver loooking into Giant netted barrel sponge {Veronguls gigantea} Cayman Islands, Caribbean Model released.

Carine Schrurs / Coral reef scenic with Barrel sponges {Xestospongia testudinaria}, Crinoids {Crinoidea}, Anthias fish Batangas, Philippines. Indo-Pacific

Alex Mustard / School of Bludger trevally (Carangoides gymnosthethus) throng over a coral reef, with a giant barrel sponge (Xestospongia muta). Misool, Raja Ampat, West Papua, Indonesia. Misool Marine Protected Area...

Alex Mustard / West Indian spider crab (Mithrax spinosissimus) shelter in a giant barrel sponge (Xestospongia muta) on a coral reef. Jardines de la Reina, Gardens of the Queen National Park, Cuba. Caribbean Sea.

Pascal Kobeh / Barrel sponge (Xestospongia testudinaria) covered with Lampert's sea cucumbers (Synaptula lamperti). Crinoids and Feather stars (Crinozoa) also on Sponge. Jewel fairy basslets (Pseudanthias squami...