I'm just down the coast from you in Santa Monica. I have found the V3i to be very stable in the stock apps in dry sand. C&J for example with the stock 10 DD coil are quite stable and go deep on the So Cal beaches. Unfortunately there is a but coming.....but if you want to hunt the wet sand and wash up area you need to use Salt Beach for sure. It helps to settle down the machine quite a bit.
The next challenge in the more populated areas is trash, trash and more trash. And in the most popular beach going areas you will also be banging coils with other detectorists as well. The public beaches are well covered each week. So don't go out there expecting to find a ring for each finger and toe, with a bag full of clad to go with it. It is more a good workout with beautiful views than a profitable venture. Most days the parking costs more than I find, but it's still fun! I don't mean to be a bummer, just trying to set the proper expectations is all. Plan on a little less and if you find a sweet spot......then enjoy it!
The Shark