Abstract: The present invention is an illumination device for use in combination with a waterbed which includes a plastic membrane which takes the shape of a mattress when it is filled with water and which is adapted to be filled with water and a frame having a headboard, four legs and base which is adapted to receive the elastic membrane after it has been filled with water. The illumination device includes a light source which is optically coupled to the water in the plastic membrane through the plastic membrane and which is mechanically coupled to the frame; and a transformer which has an on-off switch which is electrically coupled to a wall outlet and a transformer for stepping down the current through said on-off switch. The light source includes a lamp which is electrically coupled to the transformer and a prism-shape container in which the lamp is disposed and through a glass sidewall of which the lamp is optically coupled to the water in the plastic membrane.