Why a supersoaker water gun work if it is completely filled with water?

A supersoaker water gun does not work if it is completely filled with water. There must be air inside the gun in order to create pressure and force the water out of the nozzle. If there is no air inside the gun, the water will not be able to move and the gun will not work.

The amount of air that needs to be inside the gun varies depending on the type of gun and the size of the nozzle. However, as a general rule, there should be about 20-30% air inside the gun in order for it to work properly.

If you accidentally overfill your supersoaker water gun with water, you can empty it out by turning it upside down and shaking it. This will allow the excess water to drain out and the gun will work properly again.