The Seasteading Institute had to cancel their annual on-water get-together, Ephemerisle, after being quoted ridiculous insurance costs, and it came back as the unofficial Floating Festival - no tickets, no organizers, you just show up with a boat.  (Or find someone else who already has or is renting a boat and still has a spare spot, etc.)  Jul 22-25 with an unconference (i.e., show up and give a talk) on Saturday the 24th.  Posting here because of the large de facto overlap in the communities.  The location is about a two-hour drive from the Bay Area.

Main info page.