If you want fresh and casual then Quality Seafood at the International Board Walk at the Redondo Beach pier is the place. Ocean Ave. Seafood on Ocean Ave. in Santa Monica has a very good raw bar and a great happy hour for oysters. I haven't been but understand that the sister restaurant to Blue Plate, BP Oysterette also very close to Ocean Ave. Sea Foods is good for oysters too.
130 International Boardwalk, Redondo Beach, CA
Ocean Avenue Seafood
1401 Ocean Ave, Santa Monica, CA 90401
1355 Ocean Ave, Santa Monica, CA 90401