 In this video which appears to have been filmed in Germany they setup a fake "waterbed" in a mattress showroom in what appears to be a mall or some such. The waterbed is actually a square pool of water with a piece of foam placed over it so it looks like a mattress. Various different people come over to the bed and attempt to try out the waterbed which usually consists of them falling backwards onto it or just jumping on it. They expect it to catch them but since it is a fake all they get is a dousing in the pool of water. There are quite a few cameras around (which I assume are hidden) which they cut between to catch the people getting doused with water. The funniest one is the mother who falls back into it and the look on her kids face. His mouth is hanging open in awe. They must have to reset the bed after someone falls for it because the foam would be all wet and there would be water all over the floor.
Watch the full video of these people trying out a fake waterbed below or click over and view it on the host site. Source: GoogleVideo | 
