The sea thread hydroid is a colony-forming polyp. The colonies can be recognized by their long, limp, strongly branched, horny threads. Small polyps are located at the end of the branches. This species can wash ashore in massive amounts, particularly in the autumn. Another name for the sea thread hydroid is the bushy wine-glass hydroid. In Dutch, this animal has the nickname 'ape hair'. Some people say that the hair comes from mermaids.