Ships float water
When we put a piece of iron in water, it sinks immediately because iron is denser
Why should then ships made from iron and steel float in water?
This can be explained on the basis of average density' as follows.
Ship is not a solid block of iron and steel. A ship is a hollow object made of iron and
steel which contains a lot of air in it. Air has a very low density.
Due to the presence of a lot of air in it, the average density of the ship becomes less than the density of water.
Density of ship vs water.
And since the average density of ship is less than that of water, therefore, a ship floats in water. Thus, a ship made of iron and steel floats in water because its average density
is less than that of water (due to the presence of a lot of air space in it).
In fact, all the hollow objects made of dense materials (like metals) float in water because due to the presence of a lot of air in them, their average density becomes less than the density of water.
The floating of ships can also be explained in another way as follows. When a ship is placed in water it sinks to a certain level such that the weight of water displaced by its submerged portion is equal to the whole weight of the ship.
Since the ship fulfills this condition of flotation, it floats in water. Thus, a heavy ship floats because it displaces a large weight of water (which provides a great buoyant force to keep afloat).