Hairy sea mat is a bryozoan which lives in a tiny box-shaped limy skeleton. As a colony, it forms a crust often broad or star-shaped, making it easy to identify. Every individual animal has 11 to 15 tentacles. They also have an average of 9 spines surrounding the soft front end. Unless it has broken off, there is always one larger spine, light brown in color, which is one of the characteristics of this bryozoan. It's this brownish spine that gives the colony a hairy appearance, and therefore its name. As a colony, hairy sea mat resembles a cluster of colorless seaweed. Colonies regularly wash ashore. Sometimes, the beaches are strewn with huge amounts of hairy sea mat. The entire coast of Holland was covered with hairy sea mat in November 1992.