Law of the conservation of momentum.The momentum lost by 1 object is equal to the momentum gained by the object it crashes into. That is even though it doesn't damage me, it still posses a momentum and a force therefore it will still push me to the ground.When the water hits you, you are flattened hard against the ground on your stomach. Although, you take no damage.
^ Now, why is the above true?
Sorry I'm a physics student xd