Even more fun with air pressure:

if you bring a flexible water bottle with a straw onto an airplane, then before takeoff, take a big drink and re-close the bottle WITHOUT letting air enter (so the bottle is slightly concave.

If you don't do this - or if you have a rigid bottle without a bite valve - then before you open the bottle during flight, warn your seatmate of the impending geyser.

DAMHIK.