I heard a reference to this on the radio the other day… as it happens I’ve never relied on the “waterproof” part of sunscreen claims (especially when swimming or snorkeling), but always re-apply after coming out of the water every so often.
New Food and Drug Administration regulations mean that, by the summer of 2012, there will be no such thing as “waterproof” sunscreen. That’s because, frankly, there already wasn’t such a thing. A sunscreen might be more water resistant than a competitor. But you can’t assume that one application of the “waterproof” stuff will stay with you through hours of pool time. Next year, sunscreen bottles will be honest about that fact, and they’ll tell you how long you can expect water resistance to last.
The other big change: What the sunscreen protects you from. Under the new regulations, only broad-spectrum sunscreens—the kind that protect you from both the UVA and UVB wavelengths of solar radiation—with SPF values of 15 and higher, can claim to prevent skin cancer. Anything else must tell you that it’s just for preventing sunburn.