The Peacock Sea Worm is a long and thin worm that is segmented. It can be found around many of the English coasts in lower shore waters, but it is not often seen because it spends most of its time hiding in a tube. The tube is flexible and covered in mud and usually stands about ten centimetres above the surface of the seabed.

The Peacock Sea Worm can reach a length of around thirty centimetres and a width of about four millimetres. The body is a grey-purple or a yellow-orange colour and it has feathery fan-like tentacles on the top of its head which have brown, red or violet colours in them. The Peacock Sea Worm extends the tentacles out of the tube when it wants to feed and because of the shape of its tentacles this sea worm is also known as the ‘fan worm’.

Peacock Sea Worms lay their eggs directly into the water and the larvae that hatch out of the eggs first become part of zooplankton. They drift in the sea for a while before settling on the seabed to develop into adult Peacock Sea Worms.