Pressure in fluids is a funny thing. Put your thumb at the open end of a hose with water flowing through it: you'll feel high pressure. But along the sides of

Pressure in fluids is a funny thing. Put your thumb at the open end of a hose with water flowing through it: you'll feel high pressure. But along the sides of the hose the pressure from the flowing water will be a lot lower, and if you poke a hole into the side while leaving the open end open, then you might even observe that hole sucking air in!