The buoyant force on an object immersed in a liquid acts in upward direction (i.e., opposite to weight of the object).

Or in other words we can say that the buoyant force on an object submerged in a fluid is caused by the pressure difference between the top and bottom of the object. To overcome the gravitational force, the buoyant force acts in the upward direction. The larger pressure at greater depth pushes upward on the object.