when you lie on your side on the beach why is the reduction of glare small compared to being straight up?

Answer 1

..when you're wearing polarized sunglasses? Because their glare reduction depends on the angle of the lens polarization relative to the polarization of the glare. Reduction is maximum when the polarizations are at 90 degrees and minimum when at 0 degrees. These glasses are polarized such that glare from horizontal surfaces is maximally reduced when they are worn normally, on an upright head. Lying on your side you have them in the minimum-reduction orientation.