Ice
Unlike other liquids, water expands as it freezes to become ice. It floats on water because ice has less density than water. This is very unusual  most liquids gets more dense as they cool: water ice is an exception. Liquid water expands by about 9% as it becomes ice – it takes up more space. This is because the water molecules are actually farther apart instead of being closer together. The molecules in an ice crystal are arranged in a way that makes it less dense than liquid water.