All manner of concrete, steel, and stone rubble from dredging, demolition projects, and other construction is used as artificial reef materials. This material is generally available at very low cost or free from construction companies who are more than happy to get rid of it. Transportation costs determine where this material is used by the Reef Program.
12-scale worms are usually found while separating and cleaning mussels. They seem to be harmless and inoffensive. In the illustration, the head is at the left. There are many varieties, some with more or less scales.