Once, after draining my king-sized octagon waterbed (that's right octagon, with no head board) just for sh*ts and giggles, i took my hairdryer, set it on cool, and filled it with air to see if it would work for one night's rest as an air mattress, so i could wait for the next morning to fill it with new water. Needless to say, it didn't work so well (LOL).

Soooo, you can't fill a waterbed with air and expect to sleep well.