Best way to see that the curvature is to actually look at the waves.
According to FE, you should see the waves in the far off distance get smaller and smaller (blurrier and blurrier)until they vanish. The reality, however, is that they don't. You see waves up to a point with a fair bit of clarity then they abruptly stop. You know, in your mind, there are more waves across the Ocean but you can't see them even though you should be able to.