Artificial reefs in japan
In Japan artificial reefs are mainly used for substainable fishing, because the country depends a lot on the ocean as a food recource. The inhabitants of Japan already started using immense bamboo structures in order to enhance the proliferation of fish in the Middle Ages. Since that time the Japanese improved their artificial reefs a lot. They now have two mainkinds of reefs: The shallow water reefs for shellfish and seaweed, and the deeper water reefs for finfish.(Wikipedia: Japan Artificial reef)