Sea cucumberHolothuroidea

Sea cucumbers are echinoderms with an elongated, soft, and cylindrical or sausage-shaped body. Their thick, leathery skin can be smooth, warty, or covered with papillae, typically appearing in muted greens, browns, or black, though some species exhibit bright patterns. Five rows of tube feet usually line their underside. Sizes vary from a few centimetres up to 1 metre (3.3 ft) in length. They possess a ring of retractable feeding tentacles around the mouth.

They occur commonly from intertidal zones to sandy lagoons, reef flats, and slopes, generally down to 40 metres (130 ft). Sea cucumbers are detritivores, constantly processing sediment for organic particles or filtering them from the water using their oral tentacles. Most species are slow-moving or sessile. When threatened, some species rapidly contract or expand their bodies; others expel sticky white Cuvierian tubules from the anus or eviscerate internal organs, which are later regenerated.