The Floating Sensation: Why We Do Not Sink In The Pool

Why do we not “sink” in the pool? If you are someone who swims quite a bit, the answer to the question should be rather straightforward. The fact is that it is common knowledge that an object will feel lighter in water.

If you do not know what that feeling is like, put your hand into a pail of water, and you will experience that floating sensation.

What is the meaning of weight?

Weight is more than the number you see on the weighing machine. It is the measurement of which gravity attracts mass – Weight = Mass x Acceleration of gravity.

We all have probably seen sci-fi movies where the characters are able to jump effortlessly into space. This shows that weight is not constant, even if the mass is. For example, the acceleration of gravity on the moon versus Earth is different. As such, a man will weigh differently on the moon as compared to on Earth.

However, we are not discussing swimming on the moon. In fact, we do not experience that floating sensation in the water for the exact reason that we feel lighter on the moon. When we are submerged in the pool, we feel lighter because of an upward force that acts against Earth’s gravity. That upward force is known as the buoyant force, which stems from the scientific principle, Archimedes’ principle.

The origins of Archimedes’ principle

The story of Archimedes’ principle stems from the tale of an ancient king who ordered his goldsmith to make a golden crown. However, when it was made, the king did not trust the gold’s purity. Because there was no method to confirm the level of purity, the king asked a local scientist, Archimedes, to find a solution.

Archimedes came to discover the solution when he decided to take a bath. When he entered the bathtub, he noticed that the water that spilt out was proportional to his volume. Applying the same principle, he managed to find out the gold’s level of purity.

Apparent weight and buoyancy

Archimedes’ principle indicates that the upward buoyant force that is exerted on a fully or partially submerged body is directly proportional to the weight of the water that is displaced by the object.

However, what causes the upward force to be present? To understand it, we need to dive into fluid statics. The water’s pressure varies linearly with the depth of the water, meaning that the downward force acting on the submerged object is lesser than the upward force acting on the submerged object.

When an object is submerged in water, the buoyant force reacts against the object’s weight. As a result, the floating sensation that we experience is the result of the two differing forces, which is the apparent weight.

Another fascinating note is that buoyancy force differs according to the water body’s density. For example, if the object is submerged in mercury, the object will be even “lighter” than if it was submerged in water.


The world of physics is an interesting landscape. Even the most insignificant observation, such as an apple falling, could lead to the discovery of how gravity works. Needless to say, the world of physics is a place worth discovering.

If you are interested in discovering such a world, then look no further than Physics Tuition, where we educate and explore various interesting insights into the subject with our students. So, do not hesitate to contact us to get started!