The island chain of the Florida Keys parallels the edge of the continental shelf in a 150 mile long arc from Soldier Key to Key West. It forms a narrow barrier between the Atlantic Ocean on one side and Florida Bay and the adjacent bays on the other.
The islands are low-lying, and many of them barely reach a height of a few feet above sea level. The highest elevation of 18' is located on Windley Key.

   The geological formation of the upper Florida Keys, including Bahia Honda, is Key Largo limestone. This rock is derived from an ancient coral reef which consisted of similar species of corals as the present living reefs of the Keys. When sea level dropped during the ice ages, the reef became exposed, forming islands. From Big Pine Key south the geologic formation is Miami limestone which was deposited over the ancient reefs in a warm shallow sea between glacial periods.