The water bends due to the static electricity on the balloon.
Explanation:
The static electricity you built up by rubbing it against the balloon attracts the stream of water, bending it towards the comb or balloon like magic!
Negatively charged particles called electrons jump the wool to the balloon as they rub together, the comb now has extra electrons and is negatively charged. The water features both positive and negatively charged particles and is neutral. Positive and negative charges are attracted to each other so when you move the negatively charged balloon towards the stream, it attracts the water's positively charged particles and the stream bends!
