I had a floating tent once.
My son and I were doing a week (or was it 10 day) bicycle tour in Pennsylvania and were camped at a KOA a little south of Hershey when with one crack of thunder the skies opened up and it POURED. We ran back to our tent to find it floating. We picked it up and moved it to higher ground. Once the rain stopped we spent the rest of the evening running our stuff through a drier.
Similar wet wake up morning in West Virginia, Dad & I were in a Andre Jamlet French tent with a bathtub floor and we were on those huge blow up mats. I woke up and put my arms in deep water attempting to get out. Must have been ten at the time. we had floated into the top of the tent so I am guessing 12 inches of water.