Originally, sunglass manufacturers developed polarized lenses for snow skiers. The Polaroid filter when placed in a sunglass lens would kill the glare off the snow. Fishermen and sunglass manufacturers soon learned that this same polarized lens would knock the glare off the surface of water. The human eye can only focus on a narrow spectrum of light at one time. Lighter colors toward the middle of the light spectrum are the easiest to focus on while darker colors add contrast.
Glare describes any high intensity light within the visible light spectrum.
Water has reflective properties that worsen glare. Because the human eye cannot handle a wide range of different light intensities, it tends to focus on the brighter glare and thus mutes out the lower light levels. This kills the contrast required to see shapes. A polarized lens prevents horizontal glare from entering your eye by using a Polaroid filter. A Polaroid filter consists of alcohol molecules running in vertical parallel chains.