An artificial reef is a human-created underwater structure, typically built to promote marine life in areas with a generally featureless bottom, to control erosion, block ship passage, block the use of trawling nets, or improve surfing. Many reefs are built using objects that were built for other purposes, for example by sinking oil rigs (through the Rigs-to-Reefs program), scuttling ships, or by deploying rubble or construction debris. Other artificial reefs are purpose built (e.g. the reef balls) from PVC or concrete. Shipwrecks may become artificial reefs when preserved on the sea floor. Regardless of construction method, artificial reefs generally provide hard surfaces where algae and invertebrates such as barnacles, corals, and oysters attach; the accumulation of attached marine life in turn provides intricate structure and food for assemblages of fish.
National Ocean Service (NOS)
What is an artificial reef? An artificial reef is a man-made structure that may mimic some of the characteristics of a natural reef.
Can you spot the sunken ship?
In June 2002, the retired USS Spiegel Grove was sunk in waters off Key Largo. At 510 feet (155.45 meters) long, the ship was, at the time, the largest vessel ever intentionally scuttled for the purpose of creating an artificial reef.
Submerged shipwrecks are the most common form of artificial reef. Oil and gas platforms, bridges, lighthouses, and other offshore structures often function as artificial reefs. Marine resource managers also create artificial reefs in underwater areas that require a structure to enhance the habitat for reef organisms, including soft and stony corals and the fishes and invertebrates that live among them.
Materials used to construct artificial reefs have included rocks, cinder blocks, and even wood and old tires. Nowadays, several companies specialize in the design, manufacture, and deployment of long-lasting artificial reefs that are typically constructed of limestone, steel, and concrete.
Sarah Fangman, Sanctuary Superintendent, Florida Keys National Marine Sanctuary
Over the last 40 years, coral reefs in the Florida Keys, like reefs worldwide, have suffered dramatic declines. Nearly 90 percent of the live corals that once dominated the reefs have been lost. Emergency action is required to change the trajectory of the health of coral reefs in the Keys. NOAA and partners have developed an ambitious approach to restore corals at seven ecologically significant sites in the Florida Keys.