Definition; incompressible fluids and dP/dy=-ρg; demonstration of pressure in paint cans filled with air and water.
Cornelius von Drebbel's 5m submarine; overpressure; demonstrating compression of evacuated can.
Demonstration of maximum snorkeling depth; drinking from a 5m straw.
In an accelerating chamber, an apple is pulled opposite to motion, while balloon is pulled parallel to motion.
Syphoning from gas tanks; failure to blow a ping pong ball into the air; holding ball up by blowing through funnel; turbulence holds ball up.