How high can you fire the rocket? Try it and see! Pump as hard as you can to achieve a really high speed.
Pump in as much air as possible through the valve. When the valve is pressed out by the excess pressure that builds up inside the bottle, water flows out and the rocket is projected in the opposite direction along the steel wire. The force to which the rocket is exposed is known as the "force of reaction". Rockets are launched into space in a similar way.