An app which expresses the real time data of the River Thames as sound and light. A custom made and site specific sonar floats in the river near a sculpture called Liminal by artist Wolfgang Buttress. The sonar sends the real time movements of river life under the sculpture to a wi fi enabled PC. The computer subsequently transforms the live data and expresses this as an ever changing display of light and sound on the app. A musical library has been written by the musical collective BE, these individual musical stems are triggered by the activity in the water. The soundscape is constantly changing; it is fluid and mesmerising suggesting the mystery and beauty of this great river. The app is a way of making real time emotional connections with the unseen and mysterious.