A waterbed cannot be moved with water in it, full stop, since a filled bladder weighs over a thousand pounds. The entire job is draining it properly, protecting the vinyl, and breaking down the frame.
Pro tip: A faucet-mounted venturi drain adapter pulls water faster than gravity alone and is cheap; it turns a multi-hour drain into a shorter one.
Watch out: Never try to move a waterbed with any water in it; a filled mattress can weigh well over 1,000 pounds and cannot be lifted or transported.