Inlet of the Atlantic Ocean, southeastern U.S. Located along southeastern Florida, it is about 40 mi (64 km) long and 2–10 mi (3–16 km) wide; it forms part of the Atlantic Intracoastal Waterway. It is bordered by Miami on the northwest and the Florida Keys on the east. The bay was named for the early explorer El Biscaino, of Viscaya (Biscaya) province, Spain. See alsoBiscayne National Park.