There are two easy reasons the mask is fogging. First can be the initial film wasn't properly cleaned off. When you get a new mask there is residue on the tempered glass. The easiest way to get it off is using the toothpaste as mentioned above. You dip the mask in the water and then put about a pea sized blob of tooth paste on each lense. (some masks have one large one some are two split.) Rub the toothpaste all around for a few minutes. Rinse and repeat. (it's worth the extra few seconds to do it again. It is the slight abrasiveness in the tooth paste that gets the film off. Second before you dive (or snorkel) apply a pro grade anti fog. or dip. I live in FL and use 500 PSI brand. It works great for me in the warmer water temps. A small bottle is like 6 bucks, but considering what we spend to go dive, or the small amount of time we get to spend on the bottom it is well worth it. Plus you use very much. A local dive shop can give you a good rec on what will work in your area. but 3 - 7 bucks can get you more than enough for 25+ dives.