Here's why:

* Buoyant force is an upward force exerted by a fluid (liquid or gas) on an object submerged in it. This force is equal to the weight of the fluid displaced by the object.

* Liquids are fluids with a relatively high density and incompressibility. They exert a buoyant force due to the pressure difference between the bottom and top of a submerged object.

* Gases, while less dense than liquids, are also fluids. They exert a buoyant force due to the same pressure difference principle. This is why hot air balloons float, and why objects like helium balloons rise in air.

Let me know if you have any other questions!