What is the center of buoyancy?

The center of buoyancy is the center of volume of displaced water of the hull (of a vessel). Gravity pulls down on a floating object. The fluid it is floating on pushes it up and it floats (assuming it is bouyant). Both gravity and bouyancy (the two forces at work) will have an effective center. The center of gravity is not required to be lower than the center of bouyancy and in general most ship's center of gravity is above the center of bouyancy. The ship will heel until the Metacenter (which is a function of the actual Waterplane area) is at or above the center of gravity. It might be advantageous to look at the center of gravity with respect to the center of bouyancy in ship hull stability and thereby get a better grasp of the particulars. Use the link below to our friends at Wikipedia and look at some diagrams concerning the stability of ships in terms of where the centers of bouyancy and gravity are in relation to each other.