All I need do to see that earth is round, not flat, is to look up into the night sky with my unaided eye (no fish-eye lens there) and observe the moon.
Of course this must be done in a place where there is little light pollution, which means that most low-information city dwellers will not be able to do it firsthand.
Observe the moon for a few weeks, every night, and it will be obvious to anyone that the moon is a sphere illuminated by the sun. No lenses or optical tricks are necessary.
CurlyDave,
The moon has absolutely nothing to do with the assertion that WATER IS FLAT.
Stop sidetracking.
Deal with the fact that WATER IS FLAT.