Depending on size and location difficult to impossible.
More available in San Diego and Channel Islands (Oxnard), San Pedro/Long Beach. https://thelogclassifieds.com/slips-...lips-moorings/
On the right side of this page is a link to The Log's annual marina guide, start checking marina websites for wait lists and liveaboard availability. Get out your checkbook and start getting on some waitlists if you want a larger slip, if you want to be a "sneak aboard" on a 25' boat you could probably start next week.