I had both a waterbed and cats for a couple of decades, as have a couple of my friends and my brother and sister-in-law. None of us have ever had a cat puncture the bed. However, every few months one of my stud earrings would come off in the night and poke a hole! Even then, the material used for waterbed mattresses is so thick and tough, that even if there is a puncture it is almost always of the "slow leak" variety. I have never seen or heard of a house being flooded because of a poke in the waterbed. I guess it has happened, as per Wayne's post, but it must be extremely rare.