Tomales Bay

Water type: Bay
Connection to the ocean: Pacific Ocean
Continent: North America
Climate: Temperate

Largest tributaries

Tomales Bay is a long, narrow inlet of the Pacific Ocean in Marin County in northern California in the United States.

Tomales Bay is approximately 15 mi (24 km) long and averages nearly 1.0 mi (1.6 km) wide, with relatively shallow depths averaging 18 ft, effectively separating the Point Reyes Peninsula from the mainland of Marin County. It is located approximately 30 mi (48 km) northwest of San Francisco.

On its northern end, it opens out onto Bodega Bay, which shelters it from the direct currents of the Pacific (especially the California Current).

The bay is formed along a submerged portion of the San Andreas Fault. The fault divides the Point Reyes Peninsula through Tomales Bay in the north, and the Bolinas Lagoon in the south.