There are already three underwater sanctuaries along the coast: Cordell Bank, Golf of the Farallones, Monterey Bay.
Congresswoman Lynn Woolsey wants to expand them to Point Arena in Mendocino County.
The nutrient-rich water is considered a critical part of the ocean food chain.
Commercial fishing would be allowed in the area, but not oil drilling.
Woolsey says protecting the coast is good for the economy because it preserves fishing jobs and creates new ones in the tourist industry.