The Mayor of Fontana, Acquanetta Warren, goes undercover to work with firefighters, while learning how to safely handle their equipment.

Photojournalist David Handschuh recalls his experience during the September 11, 2001 attacks. He was taking pictures near the South Tower when it collapsed, which hurled him half a block and shattered his leg. He describes his experience being rescued.

Phil demonstrates buoyancy using different types of fluids and different objects. He defines fluids and explains why air and solids such as sand can both be fluids.

Water's density is 1 g/cm3. When an object with a lower density than this enters water, it floats because its downward force is weaker than the upward force exerted by the water.

Beakman explains what a submarine is and how buoyancy and density affect a submarine rising and sinking. Then he makes a DIY submarine from a soda bottle.