The short answer is yes, provided you have a waterproof case certified to the depth you plan to dive—and how long you plan to be under. Many of the best waterproof cases are suitable for submersion in up to 100 meters of water, but you’ll want to read the fine print to see how long they’re designed to withstand that. Some cases only protect your smartphone from being accidentally dropped in the water—they’re not intended for long-term underwater use—so if you plan to take your phone down with you, ensure you get a waterproof case built for it.