Light-weight, minimum-volume water pad

A low-water volume, low-weight water pad for use as a mattress or seat pad consists of a water-filled container sandwiched between an upper and lower layer of cellular foam sheets with a surrounding water-impervious sheath which is loaded through openings in the top of the sheath. The sheath serves as a flexible frame and tray for containing water which may escape from the water-filled container. The top surface of the sheath contains flaps at either end which extend beyond the opening slits in the top of the sheath. These flaps are enveloped inside of the sheath and around the bottom of the foam layer. When used as a mattress, it may be placed directly on a conventional inner spring. A rigid platform is shown which is placed between water mattress and inner spring to provide a flat surface for support of the water mattress.