PRINCIPLE
Archimedes’ Principle: a upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces and acts in the upward direction at the center of mass of the displaced fluid.
ship floats because of of buoyancy.
a ship weighing many thousands of tons - displaces a large volume (and therefore weight) of water. Hence the buoyancy force acting on the ship is much greater than the weight of the ship itself, making it to float on water.