Sand has more mass than water for the same amount of volume that is present. Dry sand has a density between 1,281 and 1,602 kg/cubic meters, and water has a density of 1,000 kg/cubic meter.
According to Convert Units, one cup in the United States is equivalent to 236.5 cubic centimeters. This is equivalent to 0.0002365 cubic meters. Calculating the mass of the water present requires multiplying 1,000 kg/cubic meter by 0.0002365 cubic meters to get 0.2365 kg of water. Calculating the mass of the sand present requires multiplying 1,281 and 1,602 kg/cubic meters by 0.0002365 cubic meters to get a present mass of between 0.3030 and 0.3789 kg. Sand, therefore, has more mass than water.