I was on vacation near the ocean last month. My own face got red even with my usual SPF. It dawned on me that salt water and sun need way more reapplication than I thought. I've started telling clients to layer it on thick if they're hitting the waves. This small shift has really helped their summer skin care.
My last beach day taught me the same lesson. I now use a waterproof sunscreen and reapply it like clockwork every hour, especially after swimming. It's a simple change but it makes a huge difference.
Wait, he only used SPF 50 in Florida in July? That's like bringing a water pistol to a house fire. The sun down there is a different beast. I can't believe he thought a single layer would cut it, even if it was high SPF. You need the waterproof kind and you need to basically bathe in it.
My buddy Jake spent a week in Florida last July. He slathered on SPF 50 but still turned bright red after swimming. The salt water just washed it right off, and he didn't reapply enough. He looked like a steamed lobster for days, which was kind of funny but also a good lesson. Now he tells everyone to put on a thick layer and do it again after every dip.
Poor Jake, that's a rough way to learn. @the_harper has the right idea with that hourly schedule. I once made the same mistake and my own lobster impression was not a good look.