In the East Bay, the reservoirs are mostly in the East Bay Regional Park system which prohibits scuba diving except by special permission. Shadow Cliffs in Pleasanton is used for classes, but that is after authorization, fees, releases, proof of liability insurance, etc.
In the summer, Dive 'N' Trips has a once a month Wednesday evening dive and potluck in Shadow Cliffs for the $6 admission fee to the park, and it's a decent after work summer dive (even if Dan can't be bothered;-) ). The first one is June 15th. Of course, if you're coming from Alameda the afternoon commute traffic is horrendous; I usually leave from Hayward before 3:00 so I don't have to sit in stop and go traffic on 238/580. The earlier in the summer, the better, as the algae increases as the water warms - I've had 15-20 feet early on, decreasing to 5' by the end of the summer.
As long as you stay close along the northern shore you'll see quite a few fish, including some large bass, as well as lots of fishing line and lures, bottles/cans, old submerged walkways, 55 gal. drums and assorted other human detritus. The water's quite warm compared to Monterey, say 73 deg. surface/64 deg. at depth with a noticeable thermocline, so I usually just dive in my 7/5 wetsuit sans hood and gloves, instead of my drysuit etc. I usually take along a goody bag and SMB and pick up what I can. I've also scored a mushroom anchor, two large beach umbrellas, a folding camp chair (blew off a fishing dock, I think) and assorted other goodies that I use. Away from the northern shore, it's a pretty empty, soft clayey bottom with a maximum depth of 45-50 feet (you have to swim almost all the way across the reservoir to get there), but there are some moderately interesting 'escarpments' and holes in the mud, as well as old tire and caterpillar tracks from when the quarry was in use.
You can head north to Berryessa or out to Folsom/Natomas, but they are not much closer than Monterey, and the visibility ranges from terrible to extremely terrible. Despite what people say, Santa Cruz has some diving, but visibility is poor 347 days per year. If you want a good time diving on a day trip or overnighter, it's Monterey/Carmel and points south, the Sonoma/Mendocino coast, or Lake Tahoe.
Other than the above mentioned sites there are various old mines and quarries in the Sierra foothills, and numerous mountain lakes other than Tahoe. Unfortunately, they share with Tahoe the fact that they're boring, as there's nothing to see other than sand/silt/trees/rocks and garbage owing to the cold, sterile water. So, Monterey/Carmel/Big Sur or the North Coast are realistically the best places to dive from the Bay Area.
It's freeway almost all the way to Monterey, about 120 miles for you, 65-75 MPH all the way, but watch those speed traps once you get into Monterey County. They are building a new courthouse using diver speeding fines.
That's about right. It takes me 1:35 - 1:40 from Hayward (100 miles) with my cruise control set at 65 (early Saturday morning, when there's no traffic), and my buddy Matt who's in Alameda makes the drive almost every Friday evening post commute in his van.
Guy
