100% waterproof with an oversize suction cup back as well as a hanger so it can be used in a shower or placed on a mirror or standard wall. The silent sweep seconds hand (no ticking) glides around the dial that show 20 second increments. These clocks are designed to ensure that when washing your hands, it is done for a full 20 seconds as recommended by the CDC for good health. Great on a boat or any high splash area or high humidity location. The dial is designed to help young people or anyone to continue to wash their hands for the recommended time. Great to be used in any public or office location as well. Uses (1) AA battery, not included.