An iceberg is a large piece of freshwater ice that has broken off from a snow-formed glacier or ice shelf and is floating in open water
Since the density of pure water ice is ca. 920 kg/m³, and that of sea water ca. 1025 kg/m³, typically, only one ninth of the volume of an iceberg is above water. The shape of the remainder under the water can be difficult to surmise from looking at what is visible above the surface. This has led to the expression "", generally applied to a problem or difficulty, meaning that the visible trouble is only a small manifestation of a larger problem.