Here's why:

* Buoyant force is the upward force exerted by a fluid (liquid or gas) on an object submerged in it. This force is due to the difference in pressure between the top and bottom of the object.

* Liquids: Because liquids are relatively incompressible, the pressure at the bottom of an immersed object is higher than the pressure at the top. This difference in pressure creates an upward force, the buoyant force.

* Gases: While gases are much less dense than liquids, they also exert a buoyant force. Although the pressure difference in a gas is smaller, it still exists. This is why objects like hot air balloons or blimps can float in the air.

Archimedes' Principle quantifies this buoyant force:

> The buoyant force on an object submerged in a fluid is equal to the weight of the fluid displaced by the object.

This principle applies to both liquids and gases.