A catchy title for a science fair project on tossing water balloons is "The Great Splash: Under Pressure." This title incorporates scientific attributes of a water balloon, keeping in mind the environmental context of a science fair.
The title should be based on the research being conducted in the water-balloon experiment. A water balloon pops because of an increase in pressure on the inside of the water balloon, causing the material to stretch beyond capacity and finally pop on impact. "The Great Splash: Under Pressure" applies to the content of the experiment and is clever enough to produce a few smiles.