My prosperous brother took me on a Hawaiian vacation a couple years ago. I saw a lot of tourists with cell phones enclosed in special zip lock waterproof bags. They took photos kayaking, snorkeling, swimming under a waterfall, etc. I was not about to risk my expensive phone. I used a Go-Pro knockoff I got for forty bucks on Amazon. It took great photos and videos.
When I would take the kids to an amusement park, with rides you can get wet in, I always took a few small ziploc bags to put my phone, car keys, and wallet into.