**Answer:** Archimedes.

**Some extra relevant information:**

The concept of buoyancy, also known as Archimedes’ principle, was discovered by the renowned ancient Greek mathematician, physicist, engineer, and inventor, Archimedes. Archimedes lived in the 3rd century BC and is considered one of the greatest scientists in antiquity.

Archimedes’ principle states that a body submerged in fluid experiences an upward force equal to the weight of the fluid displaced by the body. In simpler terms, this means that when an object is immersed in a fluid (such as water), it will experience an upward force that counteracts the force of gravity.

The discovery of buoyancy is famously attributed to Archimedes through an anecdotal event. According to the story, King Hiero II of Syracuse had given a goldsmith a specific amount of gold to make a crown. However, the king suspected that the goldsmith might have replaced some of the gold with a cheaper material. To confirm his suspicions without damaging the crown, he turned to Archimedes for help.

Archimedes pondered over the problem and eventually found a solution while taking a bath. As he immersed himself in the water, he noticed that the water level rose, and he realized that the buoyant force acting on his body was equal to the weight of the displaced water.

This insight led Archimedes to devise a method to determine the purity of the crown. He filled a vessel with water, carefully placed the crown in it, and measured the water displacement. Then, he repeated the process with an equivalent weight of pure gold. By comparing the amount of water displaced, Archimedes could determine if the goldsmith had indeed adulterated the crown.

The story may be legendary, but it showcases Archimedes’ understanding of the principle of buoyancy. His groundbreaking discovery not only had practical applications but also laid the foundation for further advancements in fluid mechanics and hydrostatics.

Archimedes’ principle is still relevant and widely used today, with countless practical applications in various fields, including shipbuilding, engineering, and even everyday objects like submarines and hot air balloons. The concept of buoyancy remains a fundamental principle that helps us understand the behavior of objects submerged in fluids.