. >> for example, many sun screens boast they're waterproof, water resistance or sweatproof, yet theoctor says those things don't mean anything, because manufacturers haven't done any testing to determine how long a product will actually last on the skin when it comes into contact with water. >> and so the problem with waterproof is that every time you go into the ocean and you're in and out, it's just going to wipe off. so i think patients have a false sense of security. >> under the fda's new guidelines, sun screens will now be labeled either water resistant for 40 minutes or 80 minutes, an indicator of when people need to reapply. dr. vana says another issue is there's no evidence with products with an spf above 50 actually give additional protection, so to comply with the new rules manufacturers will eventually stop making them. >> they'll want to use at least an spf 30. anything under that is for daily use is probably okay, but going to the beach you'll want to use at least spf 30. >> amy says she gets regular skin checkups from her doctor so he can keep an eye out on any recurr