California may be known for its beautiful, clean beaches, but the Bay Area is home to three of the dirtiest and most polluted in the state — all of them along San Francisco Bay in San Mateo County. … Lakeshore in particular is similar to Eckenbrack Park and Marlin park in that all are enclosed within a network of stagnant channels in San Francisco Bay. These channels, the report says, receive urban runoff from surrounding development and there is very little water circulation, which keeps pollution near the shoreline.