It says waterproof — can I swim for hours after applying it once?

A waterproof formula is useful for beach days and swimming because its base does not wash off as easily as an ordinary lotion. However, “waterproof” does not mean a single application keeps working all day. Water, sweat, friction and towel-drying gradually reduce the film on your skin.

After every swim, lightly towel off and put on another layer. Do the same if you sweat heavily during outdoor sport or after sitting on a towel or lying on sand—those surfaces rub against the skin and remove product. A practical pattern is to reapply at least every two hours, and any time your skin has been wet or wiped.

Even with a waterproof product, sensible sun habits still matter. The bottle is meant for face and body, so pay attention to the whole body, including often forgotten spots such as ears, shoulders, tops of the feet and the back of the neck.