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.
Steamer is an early term for any vessel power by a steam engine rather than sails.
Early steamers were propelled by large paddlewheels. "Side-wheelers", with the paddlewheels on each side, were more seaworthy, and therefore more common in ocean waters, while "stern-wheelers", with a single large paddlewheel at the back, were more common as riverboats. Later, these were replaced by more efficient screw (or propeller) vessels.