Artificial reefs, when placed on non-living bottom, can be a boon to divers and a boost to marine life. The Florida Keys Artificial Reef Association, founded in the early 1980s, has created a number of new reefs throughout the Keys from tons of concrete left over from the removal of some of the Keys' original bridges.
Decommissioned naval vessels have also been intentionally sunk at other sites. Off Plantation Key, south of Key Largo, the Duane, a 327-foot Coast Guard cutter, was sunk in 120 feet of water. Today, it's a popular diving destination. The Bibb, another former Coast Guard vessel, sits nearby.