Opposing the general rule of the nature, the ice, been solid of the water, it is lighter than the liquid, floating instead of sinking. Such fact occurs because the water becomes enlarged it making solid, phenomenon this of extreme importance for the life in the planet. It imagines if each iceberg sank as soon as was formed. Soon we would have the deep one of the oceans covered of ice. To the few, more and more ice would accumulate until great part of the water made solid. Although the ice to float, the frozen water goes down, thus guaranteeing a continuous oxygenation in the deep one of the seas, lakes, etc. the nature really seems to know what it makes.