Background on Buoyancy:
"Buoyancy" is the upward force of water that works against an object's mass -- the "buoyant force" depends on the object's volume. The greater an object's volume - the greater the amount of water it displaces and, therefore, the greater the "buoyant force".

Glossary of Terms
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• Ballast- Heavy material that provides wieght and stability. In boats, ballast is usually water. Ballast is reduced by introducing air. That's exactly how a submarine is able to float or sink!
• Boat- A floating structure, usually hollow, which is designed to carry a load.
• Buoyant Force- The upward force that acts upon an object to cause floating. When buoyant force is greater than the pull of gravity, on object will float.
• Buoyancy- The tendency of a body or object to float or rise when placed in a liquid.
• Density- The mass of a substance per unit of volume. (Think: dense objects weigh a lot but are small)
• Displacement- When an object is placed in a liquid, its volume displaces (forces out) an equal volume of liquid providing that the object does not absorb any liquid.
• Float-To sit at or above the surface of a liquid. When buoyant force overcomes gravity, an object will float.
• Keel- A long ridge directly beneath the centre of a boat's hull (bottom) that goes from the bow (front) to the stern (back).
• Propulsion- A force (such as air) which pushes a boat in a direction.
• Resistance- A force which works against another force (counteracting force). (i.e. The water itself creates resistance to a moving boat. Propulsion and the shape of the boat are specially designed to reduce the amount of resistance created)
• Sink- To sit below the surface of a liquid or at a bottom of a liquid. (i.e. when gravity overcomes buoyant force)
• Stability- A boat's ability to remain steady and balanced. A Catamaran is very stable.
• Suspension- At a point somewhere between floating and sinking (neutral buoyancy).
• Volume- The amount of space occupied by a material.
• Weight- The gravitational force acting upon an object.

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