Sleep Rating: Plush and Stable when properly filled to the top of the side rails. If waterbed mattress is properly filled at approximately 8 1/2" it is difficult to touch bottom. Entry and exit easy. Sleepers affect each other moderately. Capable of some motion, but stops within 2 to 3 seconds. The FEATHERTOP Sleep Surface has a special low tension molded top that reduces surface pressure between your skin and the mattress surface. This creates an abundance of mattress surface area, allowing your body weight to disperse across the mattress better, without raising the water level.