Preventing fog in swimming goggles and diving masks

Idea

While still dry, spit into your goggles or mask. Rub the spit with your fingers over the whole inner surface of the goggles/mask. Submerge the goggles/mask into the water for about 10 seconds. Then put them on.

Limitations and Side Effects

Once the goggles or mask get wet inside this trick does not work anymore.