An anti-fog spray market has developed to address this problem. Companies like AquaSphere, TYR, Speedo, Frog Spit and one so brilliantly named Cat Crap has anti-fogging products that work for swimmers, scuba divers, snowboarders and more.
The directions for most of these indicate to apply it to your goggles and after a short time, clean it out. It's important to clean it out—otherwise, this can get into your eyes and pretty much ruin your day.
Yes, many swimmers carry a small bottle of baby shampoo with them. Put a drop or two in each lens, wait 15 minutes, rinse it out and enjoy a fog-free swim. Seriously. Like the spray, the baby shampoo will leave a layer of transparent film on the goggle that won't let the condensation do its obnoxious thing.
This works similarly to shampoo, creating a film that blocks condensation from blocking your vision. This is a favorite tactic of the scuba diving community, but triathletes and swimmers can certainly steal the idea.
One more thing: Many goggles come with an anti-fog coating, but it wears off easy with your fingers. Avoid touching the inside of your goggles with your fingers to keep that barrier in place for as long as possible.
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