AquaTop works by projecting images onto the surface of the water. Mixed with bath salts, the water becomes milky-white and provides better contrast as a projection surface. The opaque water also reflects the infrared light emitted by a Kinect depth camera, which is responsible for tracking the position of multiple fingers – whether you hold them above the water, touch the surface from above or poke them out from beneath the surface. Both the Kinect camera and the projector are connected to a single PC.
This configuration allows for several innovative interaction modes, impossible to achieve with standard displays, such as scooping up a handful of water with a video thumbnail projected on its surface and then dropping the thumbnail over a video player area to start the video in full screen (or full bath) mode.