Wikipedia
Rigs-to-Reefs (RTR) is the practice of converting decommissioned offshore oil and petroleum rigs into artificial reefs. Such biotic reefs have been created from oil rigs in the United States, Brunei and Malaysia. In the United States, where the practice started and is most common, Rigs-to-Reefs is a nationwide program developed by the former Minerals Management Service (MMS), now Bureau of Safety and Environmental Enforcement (BSEE), of the U.S. Department of the Interior.
The program has been generally popular with fishermen, the oil industry, and government regulators in the Gulf of Mexico, where offshore platforms develop into coral reefs, and as of September 2012, 420 former oil platforms, about 10 percent of decommissioned platforms, have been converted to permanent reefs.
Opposition in California has prevented a rigs-to-reefs program on the West Coast of the US. Similarly, environmental opposition has prevented implementation of Rigs-to-Reefs in the North Sea.