;It depends. Many hardside waterbeds use the larger “California” size bed linens, while softside waterbeds tend to use conventional size linens. Some waterbed owners invest in special sheets designed specifically for waterbeds. These sheets are often stitched together at the center foot, because tucking in a standard top sheet around a heavy waterbed mattress is not easy. Waterbed sheets also include triangular corners or pockets to hold them against the mattress more securely.