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.
"DIR" or "Doing It Right" is a system of diving developed by cave divers which involves extremely rigid gear configurations and methodologies. To its adherents, DIR takes on an almost religious significance. For the true follower of DIR, no deviation may be tolerated, because DIR is perfection.
DIR is designed for cave diving. The usual object of cave diving is to go in and come back out alive. In line with this goal of accomplishing essentially nothing, DIR espouses an absolutely minimal equipment kit: "When in doubt, leave it home." DIR also espouses teamwork, mutual interdependence, and close lock-step buddy diving, things that are pretty much unavoidable in the confines of a cave anyway.