[EricH]

Originally Posted by JesseK

In order to put enough backspin on a balloon to significantly attribute to its overall distance, one would have to consider how the balloon would react to the backspin while in flight. It's not hard to setup an experiment to show this; however for the experiment to be accurate, one would need to put a true tangental force on the exact edge of the balloon so that the rotational axis is the balloon's center of mass. Since the balloon is not a rigid solid shape, the water would be pushed to the outside of the balloon and eventually form two almost identical pertrusions out of the balloon (much like how galaxies spin). As time progresses, the balloon would look like a spinning dumbell. Eventually the forces on the middle of the dumbell would be great enough to break the balloon mid-flight, therefore sprinkling the target rather than drenching it.

At least it would make some cool rainbows though

Which is about what I figured would happen. Assuming you could get a decent backspin by shortening the lower half of the barrel or some other method, and the mouth of the balloon isn't in the way, you'd get the air burst effect instead of the shell effect. At least until they make stronger balloons.