What are the mechanics of displacement boats? When submerged in liquid, the boat is exposed to the “Archimedes’ Principle,” also known as the physical law of buoyancy. This force is equal in magnitude and opposite in direction to the weight acting on the volume of liquid displaced by the vessel. Said another way, when a yacht is at sea, it moves a certain amount of water, which is equal to its weight (don’t forget, this weight includes everything, including the ballast, gas and water onboard, etc.). However, the boat does not sink because its weight is still less than the weight of the water it displaces; the hydrostatic pressure under the hull is enough to keep the vessel afloat.