Sabellaria alveolata is an annelid (ringed worm) that lives in small tubes it constructs from cemented coarse sand and/or shell material, forming reefs.

[3] These reefs range from 30 centimetres (12 in) to 2 metres (6.6 ft)[4] thick and take the form of hummocks, sheets or more massive formations.

[2] The thorax has three pairs of flattened chaetal sheaths, its chaetes form an operculum which is used to seal the tube opening.

The tubes are built from shell fragments or sand and are used to protect the worm from predators and can be repaired if damaged near the entrance.

The larvae develop in the water column and can detect the substance the adults use to bind their tubes and follow this to find a location to settle on.