The sand mason - Lanice conchilega - is a type of worm that grows up to 30cms in length. However all that is normally seen of it is this structure made of mucous and closely fitting shell fragments and sand grains which protrudes above the sand by about 5cms. It is extremely common on sandy shores all round the UK, both above and below low tide mark. It is an important food source for many wading birds.
North Sea - St. Abbs Marine Reserve