On the beach in Frinton,Essex, I always see wiggly casts on the sand and wondered if lug worm have ther habitats in sand as well as muddy shores.
Lugworm prefer a muddy sand can occur in vast numbers in sheltered bays and in the outer part of estuaries. Although some percentage of mud content is more or less essential, the species is seldom found in pure mud. It doesn't live in clean coarse sand but finer sands, in which there is a supply of organic material are readily colonised.
I think MarLIn will have more detail
all the best