A jug is filled the brim with water at 0°C. A piece of ice floats in it. The moment the ice melts.

When the ice cube melts the water level at the side of the jug is unchanged (neglecting temperature effects). The extra volume of water created due to the effect of melting is equal to the original volume (frozen state). Whether the ice cube is hollow or solid, it will displace as much water floating as it will melted.