triangular-shaped shallow body of water between the Gulf of Mexico (Mexico, Gulf of) and Biscayne Bay at the southern end of Florida, U.S. The bay, which covers about 850 square miles (2,200 square km), is partially sheltered from the Atlantic Ocean on the south and east by the Florida Keys. The average depth is about 4 to 5 feet (1.2 to 1.5 metres), and the area is scattered with small islands. Mangroves and sea grasses provide habitat for animals such as manatees and sea turtles. Navigation channels have been dredged through the bay along the line of the keys to accommodate the Intracoastal Waterway. Most of the bay is included within Everglades National Park (Everglades).