OK, now that all the amateurs have given their $.02, let's hear from somebody who actually cleans hulls for a living...
I use 3M "Doodlebug" pads to do the bulk of the cleaning. They are essentially industrial size Scotchbrite pads. They cover more territory quicker than their smaller cousins and that is of primary importance. You can get them at most chandleries. You can buy a handled holder for them as well, but these are ridiculously expensive. I make my own out of 1/8" foam PVC, the handle from a cheap mastic spreader and some marine grade Velcro. Maybe $10.00 worth of stuff, works great. Or you can always hold them in your hand. Lots of guys do.
I also go into the water with a 6" putty knife. The cheapest one Ace Hardware sells. Lasts many time longer than anything else I've used. This will shave off grass and shelled animals. Hopefully you don't find too much of either.
For the running gear, Rubbermaid makes a plastic wire brush with a scraper on the end. One of the most important tools I own.
Shaft zinc replacement will require either a flat-head screwdriver or an Allen wrench, depending on the brand of zinc you use. Attaching a wrist lanyard to either tool helps insure you don't have to go to the bottom looking for it.
Never clean a hull without wearing a hood, regardless of water temperature. The crud and bugs you take off the hull are good at finding places to hide. Don't let your ears be one of them. Don't worry too much about being electrocuted while in the water. Every marina in the state has divers working in them every day and they all go home safe at night. In 14 years of hull cleaning I have only heard one story of anybody being hurt and that was second or third hand at best. Unplug your boat from the shorepower before diving on it, though. Better safe than sorry.
Regardless of what your boat is painted with, it will need cleaning while you are in California waters. Remember that frequent, gentle cleanings are better for your paint and the environment than infrequent, more abrasive cleanings. This means every couple of months in Northern California and every 3-4 weeks in Southern California. BTW, since you plan to snorkle your way through you hull cleaning, you're gonna find out pretty quick why people pay to have it done for them.