Archimedes Principle: Explained in Really Simple Words

Archimedes principle states that if an object is submerged in a fluid, then the buoyant force acting on it is equal to the weight of the fluid displaced by that object. Buoyant force exists because pressure increases as an object goes deeper in a fluid, which, in this case, is water. Due to this, the force from the pressure exerted in the downward direction on the top of the object is LESS than the force from pressure exerted in the upward direction on the bottom of the object.
When Archmiedes got into the bathtub, he realized that as more of his body was submerged in water, the more water spilled over the bathtub’s edge. He realized that there must be a clear relationship between his weight and the weight of the water displaced by his submerged body. This was a groundbreaking idea, and one that could be applied to solve the problem of determining the purity of gold in Hieron’s crown.