Most smartphones are water-resistant, not necessarily waterproof. This means they’ll generally handle being temporarily dunked in the water, but all bets are off if they go over the side of your boat. Further, even though their phones promise to be water-resistant, companies like Apple and Samsung won’t cover them under warranty if any water damage is detected. A waterproof case will offer much better water protection—often to 10 times more depth—and guard against drops, scuffs, and scratches.