What do you feel when you see the videos like this?
You laugh probably.
Now imagin YOU are in this shop making maybe an afternoon walk. And YOU finish in this "water-bed".
What do you feel now?
I don't know, maybe these persons are actors or persons that earn some money with appearances in TV. I remember when we were students those were relatively common earnings in the universities.
If it is not so, this joke seems not a joke for me. Maybe I'm not right.