Bolinas Lagoon is an estuary, adjacent to the town of Bolinas, that opens to Bolinas Bay, a small bight between Duxbury Point and Rocky Point, located in Marin County, about 15 miles (25 km) northwest of San Francisco.
The lagoon forms a large inner harbor protected from the main bay by a spit of land known as Stinson Beach. The trough that forms the lagoon was created by the San Andreas Fault. The lagoon has a watershed of 16.7 square miles (43 sq km), with streams and canyons including Audubon Canyon, McKinnan Gulch, Morses Gulch, Picher Canyon, Pike County Gulch, Stinson Gulch, Volunteer Canyon, and Wilkins Gulch. Kent Island is located in the lagoon and is surrounded by mud flats at low tide.
The island and lagoon are part of the Greater Farallones National Marine Sanctuary. In 1972, the U.S. Congress passed the National Marine Sanctuaries Act, and the Gulf of the Farallones National Marine Sanctuary was established in 1981 and included 1,279 square miles (3,312 sq km) north and west of San Francisco Bay. The sanctuary protected open ocean, nearshore tidal flats, rocky intertidal areas, estuarine wetlands, subtidal reefs, and coastal beaches from further development. In 2015, the sanctuary expanded to encompass 3,295 square miles (8,534 sq km), with a name change to Greater Farallones National Marine Sanctuary. Read more here and here. Explore more of Bolinas Lagoon here: