It depends if the ice cube your talking about have the bigger density than the water which is 1.00G/ML then it will sink .... TO get the density of the cube u have u have to divide the mass over the volume of the cube..
Ice has a density of about 0.9 and water a density of 1.0 (by definition)
Ice floats in water with about 10% of it's volume above the surface of the liquid.
One example of ice cubes floating are...