If he finds himself surrounded by these folks at the beach he can just go in the water. I'd bet that none of them can swim.
But private land often owners appeal to the government when their beaches erode away and many times get the work to enhance and preserve their properties done. So again to be effective this would have be part of a comprehensive program. So long as bodies of water remain a commons like the air if I am going to pay for the beach I might as well have access to it.