Polarized

Polarized filters are those that only let light pass though if it's waves are oriented at a specific angle. Reflected light is polarized, so by orienting the polarized filter so that it rejects the reflected light, you get rid of glare.

Sunglasses that are polarized will significantly cut down on the glare reflecting off of the water. This makes for more comfortable vision and it aids in being able to see past the surface of the water so you can see what's underneath. Both sea and whitewater kayakers can benefit from polarized lenses.

Polarized filters on cameras also allow you to see beneath the water - good for shots where you want to show a paddler that looks like he is floating in space. As well, since the sky is filled with polarized light, playing with a polarize filter can darken or lighten a blue sky - great for bringing out clouds or getting that special effect.