Pretty sure this is a common area for shark sightings and attacks.
It’s a beautiful place - I lived there for a couple of years. However, the water is super cold and usually rough, although swimmers do go out (including my kids when they were little and would swim until their lips were blue). There are a lot of sharks, including Great Whites, in the Drakes Bay/Tomales Bay area, and every so often they get aggressive. Or hungry.