Buoyancy is a force that is felt by an object when it's partially or fully immersed i water. Even air has buoyancy. When an object is immersed in water the weight starts to decrease as the force increases with the increase in immersion. Aristotle was the first one to know this phenomenon. He was a close relative and scientific advisor of King Heron. King Heron wanted to know the purity of his gold crown. Aristotle was about to take a bath in the Common bath. As he immersed his foot in water he noticed that his leg felt lighter, something struck his mind and he ran out of the bath completely naked, shouting "Eureka!".