An artificial reef fashioned in the shape of the Southern Cross that serves as a snorkeling trail has eased traffic and reduced damage to Austrailia's Great Barrier Reef. Like the rain forests, the world's coral reefs are in peril. Artificial reefs are not a new concept, but only in the past 20 years have they become friends of the marine environment. The first artificial reefs were made from tires, appliances, sunken ships, junked cars, culverts and concrete rubble. Many do more harm than good.
Tires wash ashore.
Appliances, cars and ships leak harmful chemicals. Heavy objects damage natural reefs as currents toss and turn them over the seafloor. Today, only concrete and heavy-gauge steel are allowed in most U.S. waters. Deliberately sunk ships must be thoroughly cleaned before they are left to drown. Structures are now being designed specially as artificial reefs, and stable, non-toxic concrete is the material of choice.