Good for him, but that doesn't give him the right to restrict the liberties of others.
The point is that a person should not have the right, at least in my opinion, to buy up land surrounding what was formerly public lakes and then restrict access. Let them buy up a lot of it, but the access should be maintained.
Until it's resolved I would take the interim stand that he can't own the water, and would be encouraging fly-in operators to access it constantly with floatplanes. Wait until he gets tired of a few Cessna 180s and 185s flying in and out, props screaming away in fine pitch. And a bunch of ultra-lights buzzing their lawnmower motors over his house, (the local ultra-light schools might like to use it as an area for float training). After a while he might prefer the peace and quiet of a vehicle on a road.