Sea cucumbers are an abundant and diverse group of worm-like and usually soft-bodied echinoderms. They are found in nearly every marine environment, but are most diverse on tropical shallow-water coral reefs. They range from the intertidal, where they may be exposed briefly at low tide, to the floor of the deepest oceanic trenches. Some of the Sea cucumbers are about 20 cm in length, though adults of some species may not exceed a centimeter, while the largest species can reach lengths of 5 m . Several species can swim and there are even forms that live their entire lives as plankton, floating with the ocean currents.
