Damn. Sounds like something I would have thought of as fun...........
It used to be that a prank was a prank. Now all pranks are considered criminal behavior. I can imagine given the right set of circumstances one could be seriously injured by a water balloon falling from 8 stories up.
I remember when I was in high school I traveled to a college some distance from our town to spend a weekend. While there my friend and I got involved with a group of college friends and made a water balloon launcher using a funnel (to hold the balloon during the pre-launch), two trees, and about a dozen feet of surgical rubber tubing.
The tubing was stretched between the two trees with the funnel attached half way between. We'd then place the balloon in the funnel and pull back till the tubing was stretched to the limit, and let 'er rip! The balloon would clear the top of the nearest building and land among the diners lining up at the school cafeteria. Such fun could not be had for cheaper, I'll tell ya!
Lots of mischief making,
"Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting 'Holy Shit! What a ride!'" ~Hunter S. Thompson