Short Notes:

Ships, boats, rafts, and other objects float because of the buoyant properties of water. Like all liquids, the ocean exerts an upward pressure, which can support solid objects placed on it. In the case of ships, several factors are involved, including the density and shape of the craft and the ways in which it might be buffeted. In general, a ship will float if the volume of water that it displaces weighs more than the ship itself. The upward forces of water against the hull will overcome the downward force of gravity; this downward force may be thought of as originating from a single point called the centre of gravity. Ships are said to be stable if they can be rocked by such forces as winds and waves and return to an even keel. If a ship is improperly designed or loaded, these disturbances could lead to an unstable ship which might sink.

Click here for a Flash presentation on how ships are able to float on water.