They go North by barge, boat and whatever means they can go. Time to rethink your statment.
I have not seen any security checking papers, stopping persons from using Barge.
If anyone is worried, maybe a privatly Security co. would ensure a more secure enviorment for residences, as some resorts have done.
How hard is it for enforcement to go after those who choose boat to go north, and break into those residences on the water, in both daytine and dead of night.