Now I've heard of people being certified in Lake Folsom. Haven't personally dove there, from what I understand the visibility is very poor, which would prepare you for low visibility diving, but not ocean diving, and not much to see except for the occasional beer bottle or can from what I understand.
The viz was really bad as would be expected for a low viz research training dive with UC Davis. Also, some knucklehead was trolling in the area (we had flags up) and his lure caught me on the arm. I wasn't hurt as I broke his thin mono line. Catching a 160 lb fish on 10-15 pound test just doesn't work!