Why does a ship float in water but why does an iron nail sink in water
Whether a body will float or sink depends on the density of the body. The density of a body is the mass divided by the volume of the body.
. The density of a ship is mass of the ship divided by the volume of the ship. Although the ship is made of iron, the volume of the ship is so huge that the density becomes less than the density of water. The reason being, the ship is not a mass of solid iron. There are lots of empty spaces and other less dense substances within the volume of the ship.