According to this question, many solids will sink if they are placed in a liquid, however, when ice is placed in water the ice floats to the surface. This property can be attributed to the hydrogen bonds that forms between the water molecules.
Water is a substance that posseses properties that defines its uniqueness from all other substances. One of those properties is its DENSITY. The molecules of ice as a solid makes it less dense than water itself, it's liquid counterpart.
