How can I build an automatic, semi-automatic, multi-shot, or rapid-fire water balloon launcher?
No one has built a water balloon launcher with any sort of automation. A launcher with multiple barrels is possible, but it would be bulky and even harder to carry than water balloon launchers currently are. The only design to even include some type of automatic is Drenchenator’s Test Launcher, which meters the air but does not reload the balloons.