Occupying 172,000 acres along the southern portion of Biscayne Bay, south of Miami and north of the Florida Keys, this national park is 95% under water, and its altitude ranges from 4 feet above sea level to 60 feet below. Contained within it are four distinct zones, which from shore to sea are mangrove forest along the coast, Biscayne Bay, the undeveloped upper Florida Keys, and coral reefs. Mangroves line the mainland shore much as they do elsewhere along South Florida's protected bay waters. Biscayne Bay functions as a lobster sanctuary and a nursery for fish, sponges, and crabs. Manatees and sea turtles frequent its warm, shallow waters. Unfortunately, the bay is under assault from forces set on a course of destruction.