The Honeycomb Sea Worm is a segmented dark brown or black sea worm that has three pairs of flattened bristles on its body. It can be found along the south and west coasts of England and sometimes on the south-east and east coasts. It lives on exposed beaches which have half buried rocks, fine sand and fine shell segments, but it is very rarely seen. It lives with other Honeycomb Sea Worms to form a colony.

The Honeycomb Sea Worm is around four centimetres long and has a rounded head with short tentacles that catch food and pass it to the mouth. Honeycomb Sea Worms build tubes by gluing fine sand and fine shell segments together and they often hide inside these tubes. An individual tube can be up to twenty centimetres in length and all the tubes squashed together seem to create a large honeycomb-looking colony. Some colonies can be two or three metres wide and a metre deep.

The female Honeycomb Sea Worm can lay thousands of eggs at a time and the larvae hatch out directly into the water. They first become part of zooplankton for six weeks or as long as six months and then settle onto established colonies where they build their own tubes to live in.