The Trembling Sea Mat is a yellowy brown sea creature that looks similar to a moss-like plant than an animal. The Trembling Sea Mat is very rare in England and can only be found in shallow waters in a lagoon at Swanpool in Cornwall. It attaches itself onto stones, shells and wood.

The Trembling Sea Mat is made up of different ‘zooids’. The zooids are small cylindrical–shaped organisms with a mouth and tentacles. These organisms form a colony in the shape of a knotted mat of stems and this is why it has the name ‘Sea Mat’. Zooids can be about one to three millimetres in length and each zooid has a ring of eight hair-covered tentacles around its mouth. It uses its tentacles to filter micro-algae when it wants to feed. Zooids have different functions in the colony so they can survive as a whole. Some zooids gather food, some defend the colony, some keep it clean and some reproduce.

Trembling Sea Mat release their eggs around June to September and the larvae that hatch out of the eggs become part of zooplankton for a while. Eventually they settle to develop into young zooids. Young zooids link together to create a chain-like stem called a ‘stolon’. Stolons grow from the base of new zooids and they grow horizontally along the ground to form a mat of stems.