Sarasota Bay is a lagoon located off the west coast of Florida in the United States. Though no significant single stream of freshwater enters the bay, with a drainage basin limited to 150 square miles in Manatee and Sarasota Counties, it is generally treated as an estuary, with three "passes" or inlets, giving access from the Gulf of Mexico. Its source of freshwater has been increased from natural historical levels by urban surface runoff.