Buoyancy also known as buoyant force is the force exerted on an object that is wholly or partly immersed in a fluid. Buoyancy acts upward for the kind of situations encountered in everyday experience.
It is caused by differences in pressure acting on opposite sides of an object immersed in a static fluid.
1.The pressure on the bottom of an object is greater than at its top (because pressure increases with depth).
2. The force on the bottom pushes up and the force at the top pushes down (since force is normal to the surface)
3. The direction of the net force due to the fluid is upward.