Water-resistant sunscreen lasts 40 or 80 minutes.

That’s it. Those are the only two durations the FDA allows. If the label says “water-resistant (40 min)” it protects for 40 minutes in the water or while sweating. If it says “80 min” you get 80 minutes. There is no “all day” or “waterproof” — those terms aren’t allowed because they’re lies.

Water-resistant means the sunscreen has been tested to stay on wet skin for that amount of time. After that, you need to reapply. Doesn’t matter if you barely got in the water; the clock is running from the moment you get wet or sweat.

If you’re just sitting under an umbrella and not swimming, you still need to reapply every two hours (or after towel drying). The water-resistant claim only matters for water activities. So check the bottle for the number — 40 or 80 — and set a timer. Your skin won’t argue.