In Ratzeburg, we very much enjoyed our daily early morning swims. One thing that is really nice to observe when you are swimming in a calm lake is how things vanish behind the horizon. Of course, you see the same effect when sitting on the beach or on a boat, but somehow it impresses me most when I’m either in the water or lying flat on my belly on a surf board.
For buoys or boats a little further away it is very difficult to see the water line.
The boats in the picture above are maybe about half a kilometer away. Ignoring all effects of refraction of light and just looking at the geometry, the bottom 20 cm of the boats should be missing – which fits well with what we observe. Nice!