Myth No. 4: Waterproof lotions don't need to be reapplied
The American consumer is lazy. Sorry, but we are. So when we see words like "waterproof" and "water resistant," we don't consider that they are not synonymous, nor do we try to figure out what those terms really mean.
According to the FDA, "water resistant" sunscreen must keep working for 40 minutes in the water. To be "waterproof," the lotion doesn't have to be good all day -- it only has to last for 80 minutes.
If you only intend to be outside for 80 minutes, then -- yes -- waterproof really does last all day (water resistant gave it up more than half hour before that).But if you're going to be out there for 81 minutes or more, you have to reapply the waterproof stuff.