well, supposing you are looking at a beach that is at sea level, you are only standing about 10-15 feet ABOVE sea level, that would mean that, although you SHOULD be able to see at least something of the beach, the trees would be much more prominent since they are not only AT sea level but much taller than your perspective,
also, I do believe that the curvature of the earth could be doing it's thing and the beach could be edging it's way beyond the horizon, leaving only the trees in view
