surface tension

The buoyancy provides an upward force on the object. According to Newton's first law of motion, if the upward forces (including the buoyancy) balance the downward forces (including the weight) the object will remain at rest. Otherwise, it will accelerate upwards or downwards.

here water wets the surface of the cube completely, so there is no additional distance by which it is buoyed up and down,because If the buoyancy equals the weight, the body has neutral buoyancy and may remain at its level.