Bouyancy is the apparent upward force produced on a body by an enveloping fluid. The discovery of the "law of buoyancy" is attributed to Archimedes (and is often referred to as Archimedes principle), who declared "Any object, wholly or partly immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object".
In a static fluid, a body therein submerged will be subjected to a upward acting force of a magnitude equal to the weight of an equivalent volume of the fluid.
See main article, centre of buoyancy
Buoyancy is a force vector, whose direction is opposite of gravity. This vector radiates from the centre of buoyancy of the submerged object: the centroid of the submerged volume. The magnitude of this vector will be equivalent to the magnitude of the force of gravity on the equivalent displaced volume of working fluid. The centre of buoyancy is given by the co-ordinates of LCB, TCB, and VCB (longitudinal, transverse, and vertical centres of buoyancy).
When a vessel is at rest (static equilibrium), the centre of gravity and the centre of buoyancy will be aligned vertically, with equal magnitudes. For a vessel to float, it must displace enough fluid (by mass) to support its own mass. This equivalent mass is the vessels floating displacement.