You head out to the beach or plan a day by the pool. Not wanting a dip in the water to remove your sun protection you make sure to apply a spf product that won't wash off during a swim. Good plan...except...
While the sun product may, in fact, resist washing away its effectiveness for actual UV protection lasts no longer than any other product with a similar spf rating. You may feel the presence of your waterproof sunblock—the typical greasiness remains on the skin—but your two-hours of safety is now up regardless of whether you can detect the product by feel or not. Sort of like chewing gum that's lost its flavor but is still chewable.
Many people wrongly believe that waterproof sunblocks last longer than those not claiming serious water-resistance. Don't be fooled! If the sun is up and you are out under it be safe and reapply every two-hours for maximum efficacy. Such a nice way to avoid the MOHS surgeon!
Have a fun and SAFE summer!