Heal The Bay presented its 21st annual beach report analyzing more than 400 coastal areas.
Ninety percent of the beaches got good ratings, and Ocean Beach at Balboa was rated among the cleanest. But Baker Beach is the only coastline in the Bay Area to be rated among the worst for water quality.
Cowell Beach in Santa Cruz county topped the "beach bummer list" while Capitola Beach rounded out the top 10. The problem with Baker Beach is the runoff from Lobos Creek.
"You should look at the beach report card and maybe avoid swimming or going to this particular beach and swimming right in front of the creek area, versus upshore or just downshore," said Amanda Griesbach, a beach quality scientist for Heal The Bay.
This year, the beach report was also extended to Oregon and Washington. In general, coastal beaches were cleaner than bayside areas because of the runoff from water treatment plants.