The Florida Keys are a chain of islands extending 320 km (199 mi) along the southern edge of the Florida Plateau from Biscayne Bay to the Dry Tortugas (101 km [63 mi] west of Key West). The Florida Reef Tract, a band of living coral reefs paralleling the Keys, extends from Fowey Rocks to the Marquesas and includes about 130 km (81 mi) of bank reefs and 6,000 patch reefs. For convenience, the Keys