San Fran Bay you can see a great distance while under water.
Visibility varies greatly in San Francisco Bay depending primarily upon the weather. But nobody who has ever spent a minute in the water here would say you can see a "great distance."
I will not defend divers I have never met, working in a waterway that I have never seen. But I find it very difficult to believe that all, or even most, of the dive services in the Cheasapeake Bay Area are doing the poor quality work several have described as "typical" in this thread.