The mushroom anchor is suitable where the seabed is composed of silt or fine sand. It is shaped like an inverted mushroom, the head becoming buried in the silt. A counterweight is often provided at the other end of the shank to lay it down before it becomes buried. A mushroom anchor will normally sink in the silt to the point where it has displaced its own weight in bottom material, thus greatly increasing its holding power. These anchors are only suitable for a silt or mud bottom, since they rely upon suction and cohesion of the bottom material, which rocky or coarse sand bottoms lack. The holding power of this anchor is at best about twice its weight until it becomes buried, when it can be as much as ten times its weight. They are available in sizes from about 10 lb up to several tons.
