This is a point of contention in Rhode Island where (I think) the state constitution says that coastline, defined as a place that the tide regularly covers and uncovers, is public land. I believe the original intent was to preserve access for fishing. Lots of wealthy people who own waterfront property go to great lengths to prevent access to the shoreline between their property and the sea. Even in instances where the state has declared the public can walk over a specific privately-owned seawall or down paths to access the shore, landowners hire security guards, install elaborate alarm systems, puncture tires, and generally do whatever they can to harass anyone trying to legally exercise their rights. It's pretty pathetic.