Bolinas Lagoon is a tidal estuary

Estuary

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

, approximately 1100 acre (4.5 km²) in area, located at 37.918°N 122.681°W in the West Marin

West Marin

West Marin is the largest rural region of Marin County, California.The West Marin Chamber of Commerce includes seven unincorporated communities in its definition of West Marin: Point Reyes Station, Olema, Stinson Beach, Bolinas, Tomales, Dillon Beach, and Inverness...

 region of Marin County, California

Marin County, California

Marin County is a county located in the North San Francisco Bay Area of the U.S. state of California, across the Golden Gate Bridge from San Francisco. As of 2010, the population was 252,409. The county seat is San Rafael and the largest employer is the county government. Marin County is well...

, United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. It is a part of the Gulf of the Farallones National Marine Sanctuary

Gulf of the Farallones National Marine Sanctuary

The Gulf of the Farallones National Marine Sanctuary is one of 13 marine sanctuaries in the U.S., found outside San Francisco's Golden Gate surrounding the Gulf of the Farallones-History:...

. The lagoon is a back bay of Bolinas Bay

Bolinas Bay

Bolinas Bay is a small bay, approximately 5 miles wide, on the Pacific coast of California in the United States. It is in Marin County, north of the Golden Gate, approximately 15 miles northwest of San Francisco...

 on the Pacific

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

 coast approximately 15 mi (25 km) northwest of San Francisco. The trough in which the lagoon sits was formed by the San Andreas Fault

San Andreas Fault

The San Andreas Fault is a continental strike-slip fault that runs a length of roughly through California in the United States. The fault's motion is right-lateral strike-slip...

 which runs directly through it. The lagoon is separated from the main bay by a small spit of land, known as Stinson Beach. The sand bar that encloses this lagoon is full of beachgoers and surfers on hot days, seeking to escape both heat and the urban Bay Area

San Francisco Bay Area

The San Francisco Bay Area, commonly known as the Bay Area, is a populated region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses metropolitan areas of San Francisco, Oakland, and San Jose, along with smaller urban and rural areas...

.

Bolinas Lagoon is on the list of wetlands of international importance

Ramsar list of wetlands of international importance

This is the list of wetlands of international importance as defined by the Ramsar Convention for the conservation and sustainable utilization of wetlands, recognizing the fundamental ecological functions of wetlands and their economic, cultural, scientific, and recreational value.The Convention...

 as defined by the Ramsar Convention

Ramsar Convention

The Ramsar Convention is an international treaty for the conservation and sustainable utilization of wetlands, i.e., to stem the progressive encroachment on and loss of wetlands now and in the future, recognizing the fundamental ecological functions of wetlands and their economic, cultural,...

 for the conservation and sustainable utilization of wetlands. Portions of the lagoon are included in Bolinas Lagoon County Park, and the western shore is part of the Golden Gate National Recreation Area

Golden Gate National Recreation Area

The Golden Gate National Recreation Area is a U.S. National Recreation Area administered by the National Park Service that surrounds the San Francisco Bay area. It is one of the most visited units of the National Park system in the United States, with over 13 million visitors a year...

.

Bolinas Lagoon has a 16.7 square miles (43 km²) watershed. Streams and canyons feeding into it include: Wilkins Gulch

Wilkins Gulch

Wilkins Gulch is a valley in western Marin County, California, United States, located northwest of Pike County Gulch. It is associated with a small stream....

, Pike County Gulch

Pike County Gulch

Pike County Gulch is a coastal valley in Marin County, California, United States, which is associated with a small stream. It is located between Wilkins Gulch and Audubon Canyon ....

, Audubon Canyon, Picher Canyon, Volunteer Canyon, Morses Gulch

Morses Gulch

Morses Gulch is a coastal valley in Marin County, California, United States.It descends the western slope of Bolinas Ridge and drains into Bolinas Lagoon.-See also:* List of watercourses in the San Francisco Bay Area...

, McKinnan Gulch

McKinnan Gulch

McKinnan Gulch is a valley in Marin County, California, United States.It contains a small stream which descends the western slope of the Bolinas Ridge and drains into Bolinas Lagoon....

, and Stinson Gulch

Stinson Gulch

Stinson Gulch is a valley in Marin County, California, United States which is associated with a small stream.The stream descends the western slope of the Bolinas Ridge, crosses State Route 1 just north of Stinson Beach, California, and drains into the southern tip of Bolinas Lagoon.Most of Stinson...

. Kent Island

Kent Island (California)

Kent Island is a small island in Marin County, California. The island is included in the Gulf of the Farallones National Marine Sanctuary.-Location:The island is located within the Bolinas Lagoon, a salt water inlet of the Pacific Ocean...

 is located in the lagoon.

The lagoon is considered to be among the possible landing spots of Francis Drake

Francis Drake

Sir Francis Drake, Vice Admiral was an English sea captain, privateer, navigator, slaver, and politician of the Elizabethan era. Elizabeth I of England awarded Drake a knighthood in 1581. He was second-in-command of the English fleet against the Spanish Armada in 1588. He also carried out the...

 on the coast of North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

in 1579.