The RV Whisper Water Leak sensor is an oval puck-shaped device that is placed on the floor where water leak detection is needed, such as under bathroom and kitchen sinks. The sensor requires an RV Whisper Monitoring Station (sold separately). The Water Leak sensor stands on 3 small metal feet that detect when there is water between the metal feet. When water is under the sensor, it sends out a Bluetooth Low Energy message that is captured and logged by the RV Whisper monitor station along with the following timestamps: Just Got Wet, Still Wet, and Just Got Dry.