Any of the 1100 species of marine invertebrates from class Holothuroidea of the phylum Echinodermata; all have soft cylindrical bodies and are found mainly in shallow tropical waters. Many species are edible, particularly those of the genera Stichopus and Cucumaria. A popular delicacy in some Asian countries, where they are normally gutted, boiled and dried prior to consumption. Also known as sea cucumbers.