California diving isn’t so much about agency affiliation and related or agency specific dive clubs. In other words there are no BSAC specific clubs or PADI dive clubs or NAUI specific clubs etc.
The closest dive certification agency affiliated club mentality and dive scene would possibly be GUE? I don’t know if it’s so much that way anymore.
Generally you just get on a boat and write down your cert info on the sheet when you board, and find a slot on the bench to put your stuff. A lot of them will let you solo and or if you want/need a buddy they will set you up. It’s pretty lax. They don’t care what agency your certified through as long as it’s ligit and you know how to dive. If you want nitrox they will want to see a card for that.
You can always shore dive too and find buddies at the LDS or social media, at the dive site, etc.
And then yeah, dive clubs. But they don’t care what your certification agency is as long as you know how to dive.