Iceberg

The word "iceberg" is a partial loan translation from Dutch ijsberg, literally meaning ice mountain, cognate to Danish Isbjerg, German Eisberg, Low Saxon Iesbarg and Swedish/Norwegian Isberg.
Overview
Because the density of pure ice is about 920 kg/m³, and that of sea water about 1025 kg/m³, typically only one-ninth of the volume of an iceberg is above water. The shape of the underwater portion can be difficult to judge by looking at the portion above the surface. This has led to the expression "tip of the iceberg", for a problem or difficulty that is only a small manifestation of a larger problem.