It is a business so to me if they sell food or drink its just rude to walk in an sit on their chairs with a cooler. If you can assess access the beach without going across private land I would say a part of the beach is public up to that high water line , but depending on where that high water line is certainly their is beach that is on private property and they have the right to control that as private. Obviously if the sand goes right up to a bar, hotel, condo or home it does not mean its is public to use or be on.