The savvy reader knows that you should never leave your valuables unattended on the beach. So what are you to do with your money, car keys, room keys, license, credit cards, etc? How will you keep them dry when you snorkel, kayak, swim, etc? Store them in a floating waterproof carry case or dry sack.
You can search for waterproof cases and dry sacks online. (REI sells dry sacks online. For example, here’s what one search turned up.) You can also check in your local stores like Wal-Mart and Target. As summer swimming gear is arriving in stores, this is a good time to look for waterproof cases. Oddly enough I found the floating waterproof case shown in the photo at my local Kroger grocery store.