DIRECTIONS: First, wedge a paper napkin tightly in the bottom of a clear plastic glass or cup. Now turn the glass so its rim is down and sink it straight into the water, being careful not to tilt the rim. If the trick is done right, the trapped air will prevent the water from entering the glass, and the napkin will stay high and dry.

NOTE: The diving bells of old operated by the same principle. In essence, they were huge metal cups that held a bubble of air for the divers to breathe.