There are plenty of local ordinances that would never survive legal
scrutiny but they survive because nobody wants to actually fight them
in court. This is particularly true in places where the sand meets the
sea and they probably don't have jurisdiction in the first place.

Hmmm. Florida Statutes 327.60(2) reads:

"... local governmental authorities are prohibited from regulating the
anchorage of non-live-aboard vessels engaged in the exercise of rights
of navigation."

Obviously, every little town would want to outlaw any outside boats and
keep their little private ocean. Does excluding the entire beach count as
"anchorage" or the "rights of navigation"?