Bill Nye explores the science of hydrodynamics to explain the concept of buoyancy. The science guy examines displacement, or substitution reactions, by performing several experiments to illustrate how objects stay afloat or sink. Live-action footage of mini-submarines and scuba divers is used to demonstrate negative and positive buoyancy. Also explains how buoyancy enables hot air balloons to take flight .

Award-winning series explores the world of science and nature using humor, music, experiments, and interviews with scientists. DVD features fully indexed chapters correlated to National Science Standards, downloadable teacher's guide, interactive glossary and quiz, Internet links, and bonus materials.

1. Big idea -- 2. Try this : shape and buoyancy -- 3. Way cool scientist : wet submarine -- 4. Big demo : what floats -- 5. Music video.