Your goggles will start fogging up if you’re not careful, and the reason is simple. Your face (inside the goggles) is warmer than the area outside of the goggles—in this case, the water. Condensation creates fog that is a pain in the butt for swimmers in the middle of a hard workout or, even worse, a race.
This is an issue as old as goggles, and stories have been passed around the triathlon and swimming circles on how exactly to combat this nuisance.
Here are some of the more common solutions