Yeah, this is disingenuous. No-one is requiring him to have liability insurance for beachgoers, and it'd be a pretty laughable attempt to sue him for any incident at the beach.
The insurance is not likely for the surf side of the beach but for the area above high tide and the access to the beach.
I think you'd have a fairly good case that you could not be held liable for for injury that occurred on an easement (actually, scratch that, I changed my mind and IANAL... given that an easement is non-possessive, you still own the property... but at what level are you required to make it safe?)
I don't know the pertinent CA laws, but in NY you can be fined for not shoveling snow off of your sidewalk and you are required to keep the sidewalk in good repair. If the sidewalk is broken and somebody trips, you can get fined by the city and/or sued by the ankle breaker. If it needs to be replaced, you're expected to do it yourself with your own money or be fined.