Almost everyone of us would have seen ships and boats sailing in water but how many of you ever thought about the science behind it. Isn't that strange to know that heavy steel ships don't sink in water whereas a small metallic pen sinks down? So, why do ships not sink in water, read on to find out.

No doubt the floating boats have signs of some Supernatural creator in them. He holds the heavy navigational traffic in water. But what is the mechanism behind it?

Mechanism Behind Floating Ships

Two main factors in ship design keep the ship floating:

1. Weight of ship (loaded and unloaded).

2. Shape of ship.

The ship designers calculate the weight of loaded ships and compare it to the weight of the water that will be displaced when the ship is placed in the water. The more water that is displaced, the higher the ship will float (i.e. in theory, if you keep loading a ship, its weight will exceed the weight of displaced water and it will sink).


The tendency of a body to uplift an immersed body, because of the upward thrust of the liquid, is known as Buoyancy. The force tending to uplift the body is called the Force of Buoyancy or buoyant force and is equal to the weight of the liquid displaced. When a body is immersed wholly or partially in a liquid, it is lifted up by a force equal to the weight of liquid displaced by the body. This statement is known as Archimedes Principle.

According to Archimedes Principle:

An object floats when it has displaced its weight in the medium, in which it is floating. A large ship is hollow and big and easily displaces its weight in the ocean or fresh water. That's why it floats easily and not sinks in water.


1. If the force of buoyancy is more than the weight of the liquid displaced, then the body will float.

2. If the force of buoyancy is less than the liquid displaced, then the body will sink down.

More simply, if the volume of water displaced is more than the volume of object, the object will float.

Now you know why ships don't sink. That was interesting to learn about Buoyancy, that's the law create by God, this is indeed very amazing.

Tag: why does a ship not sink in water