Biscayne Bay supports a wide variety of plants and animals, some of which are important for fisheries. Many rare, threatened and endangered species inhabit this estuarine ecosystem including manatees and crocodiles. On the east side of Biscayne Bay, several miles off the coast, lie the barrier islands. Along the mainland shoreline of Biscayne Bay lies the longest stretch of mangrove forest on Florida's east coast. Inland, hardwood hammocks grow with lush exotic plants and trees.
Seagrasses grow in beds throughout the bay wherever conditions are favorable.
The Biscayne Bay watershed also includes 83,000 acres of agricultural lands to the southwest. Vegetables, tropical fruit and nursery plants are grown within this agricultural area. Biscayne Bay is a shallow, subtropical estuary with a natural depth ranging from three to nine feet. Much of the upper bay has been modified and dredged, so that depths now average six to 10 feet and include some dredged areas and channels up to 40 feet deep. A basin of about 840 square miles drains to the bay.