Coin sinking in water. Gloved hand placing a British one pound coin into a dish of water. A pound coin is made of copper, zinc and nickel, and is some 7.6 times denser than water. As it is more dense, it sinks to the bottom of the dish. For a repeat of the demonstration with mercury in the dish, see clip K003 3930. For the same demonstrations using a brass screw, see clips K003 3931 mercury and K003 3936 water.