Waterbeds, water beds furniture and water bed mattress. Water bed fill with water. Waterbeds primarily consist of two types, hard-sided beds and soft-sided beds. A hard-sided waterbed consists of a water-containing mattress inside a rectangular frame of wood resting on a plywood deck that sits on a platform. A soft-sided waterbed consists of a water-containing mattress inside of a rectangular frame of sturdy foam, zippered inside of a fabric casing, which sits on a platform. The effect is to look like a conventional bed and is designed to fit into existing bedroom furniture. The platform usually looks like a conventional foundation or box spring, and sits atop a much-stronger-than-normal metal frame.