I don't have a water bed, but I imagine you'd need to use under the bed restraints. You could probably bolt something to the floor to attach restraints too, but that's pretty extreme. What about the side of the bed? is it in a wood frame that you could bolt an attachment to? You'd have to be careful to not go through and destroy your water bed though. Good luck!

What you need is a "D" ring with a strap for mounting, something like this-


Use wood screws to attach it to the inside of the waterbed frame, I would mount it down low towards the bottom so it is out of the way. All you will need then is a restraint that some kind of clasp can be used to attach it with.

Thanks for the info. I'll definitely have to have my bf install those into the wooden frame. Would hardware shops have the d-ring or would I have to special order them?

ohh good q. i never thought about how that would work with a water bed. once you figure it out, i bet its awesome tho!