Sea fans are composed of numerous polyps that grow together in a flat, fanlike pattern. In sea fan colonies, each polyp has eight tentacles, and they spread these out to form a net for catching plankton. An internal skeleton, composed of a scleroprotein called gorgonin, supports the branches while the polyps form a layer over the entire surface. Most sea fans grow to roughly 60 cm in height and are found in the shallow waters of all oceans.