Sunscreen use is one of the easier healthy habits you can have during the summer, especially since you're going to be ruining your body with copious grilled meat and alcohol consumption -- all you have to do is go into your local drugstore, buy a bottle, spray or wipe it on, and you'll never get cancer, right?
Spoiler: wrong. For starters, sunscreen doesn't protect you against all forms of skin cancer, which is supposed to be its big selling point, right? And if you re-apply continuously -- which is what mom told you to do, right? -- you may just be rubbing potentially harmful chemicals into your skin.
This doesn't mean you should avoid rubbing on some sunscreen before you pass out on the beach. It just means you should be smarter about the kind of sunscreen you do buy.