Sea cucumbers are echinoderm

Echinoderm

Echinoderms are a phylum of marine animals. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone....

s from the class

Class (biology)

In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

 Holothuroidea.
They are marine animals with a leathery skin and an elongated body containing a single, branched gonad

Gonad

The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...

. Sea cucumbers are found on the sea floor worldwide. There are a number of holothurian icon species and genera, many of which are targeted for human consumption. The harvested product is variously referred to as trepang

Trepanging

Trepanging is the Anglicisation of the act of collection or harvesting of sea cucumbers, known in Indonesian, as "trepang".The collector or fisher of trepang is coined a trepanger....

, bêche-de-mer or balate.

Like all echinoderms, sea cucumbers have an endoskeleton

Endoskeleton

An endoskeleton is an internal support structure of an animal, composed of mineralized tissue. Endoskeleton develops within the skin or in the deeper body tissues. The vertebrate is basically an endoskeleton made up of two types of tissues . During early embryonic development the endoskeleton is...

 just below the skin, calcified structures that are usually reduced to isolated microscopic ossicles (or sclerietes) joined by connective tissue.