Have you ever seen a hot air balloon? Personally, I find them terrifying, but I always see a few every year while I'm enjoying time at my cottage on Keuka Lake. Well, it turns out that hot air balloons actually float through the air due to buoyancy, which we generally associate with water.
This is based on Archimedes' principle, which says that an object of any shape that is suspended in a fluid is acted on by an opposite force equal to the weight of the fluid displaced by the said object. So a hot air balloon floats in the air using the same idea as an object that floats in water.
In a hot air balloon, the buoyant force is generated by heating the air inside of the balloon, which makes the air less dense than the cooler air around it. This creates a buoyant force and lifts the hot air balloon into the sky as if it were an object less dense than water floating at and above the surface. What is even cooler is that the balloon has enough hot air in it to create enough lift to carry the gondola and the passengers riding along!! Cool!