Very cool. 1/8000 is pretty good for freezing the motion of water. Although at this point the snapping back of the balloon is moving the water more than gravity. It really is hanging in the air like while-e-coyote at this point.
The downside to this is that you have to open the lens up a lot and loose depth of field. The blurs aren't motion but just drops going away from the focal plane.
Most of the popping water balloons you see are done with a hiviz sound trigger kit. When it hears the balloon pop it starts a timer and then fires a flash in the dark or semi-dark.
My Canon 580exII on manual setting at 1/128th power produces a pulse about equal to 1/30,000 to 1/40,000 of a second. It will still work with any flash, and nicely the cheaper the flash usually the smaller the capacitor and the faster it can flash.
The sound kit is not that expensive and very easy to build, no soldering required. So if you have a flash (Even a cheap one) you could try that method.
I realize you were trying to show how fast the camera is... I just wanted to point out that if people like this kind of photography, this is a good way to go. You can even freeze the balloon in mid-pop and see it tear open and understand why its springing back away from the stick and shooting off the other way. Its just like a big round rubber band gun, with inertia serving as your finger holding the other end.
Fast stuff is cool!
Even if you dont get the kit, check out the hiviz site. They have lots of example pictures of high speed photography.