There is no evidence you should reapply sunscreen every 2 hours.

It’s incredible how many consensus guidelines dissolve when you look closely at them. If you listen to any authority on the subject of sunscreen, you will hear it endlessly repeated that you absolutely must reapply sunscreen every 2 hours while you are in the sun, and immediately after swimming, sweating, or exercising. Not only that, you’ll hear that you need to apply sunscreen before going outside, even if you put it on earlier and stayed indoors.