If you’re doing something that makes you likely to be sued, your insurance company would want to know about it (homeowners, liability umbrella policy?). They may be able to help you with the appropriate forms. You don’t want to get in a situation where you are being sued and your insurance co. denies coverage. As stated above, you will be sued, not by divers, but by their heirs, and defending that waiver could get pretty expensive. The waiver doesn’t really keep you from being sued. It is your defense in depositions, court, etc.