How can a concrete or metal boat float?

A concrete or metal boat can float due to the principle of buoyancy, which states that an object will float if it displaces a volume of water equal to its weight. Although concrete and metal are denser than water, boats made from these materials are hollow or have a shape designed to displace enough water to support their weight. This design creates a situation where the overall density of the boat, including the air inside it, is less than that of water, allowing it to float.