The Sea Mouse is an unusual looking marine worm, although it really doesn’t look like a worm. Its body is covered in a dense mat of bristle-like hairs which gives it an almost mouse-like appearance and this is why it has the name ‘Sea Mouse’. It is widespread around the English coast and can be found in shallow water and in water as deep as a thousand metres. However, it is very rarely seen as it buries itself head first in the sand.

The Sea Mouse can grow up to a length of around twenty centimetres and the bristles on its body are usually a deep red colour, but when light shines on them they can have a vibrant blue, green, yellow or bronze sheen to them. It is very difficult to recognise the head, but sometimes two-horn like organs can be spotted at the front of its body. It uses these organs when it wants to feed.

The female Sea Mouse is believed to carry her eggs under her body for a short while and then releases them directly into the water where they hatch. It is not sure whether the larvae become part of zooplankton for a short time or just settle immediately on the seabed to develop into adult Sea Mice.