<P> An iceberg or ice mountain is a large piece of freshwater ice that has broken off a glacier or an ice shelf and is floating freely in open water . It may subsequently become frozen into pack ice (one form of sea ice). As it drifts into shallower waters, it may come into contact with the seabed, a process referred to as seabed gouging by ice . About 90% of an iceberg is below the surface of the water . </P> <P> Icebergs are possible on Earth because of an unusual property of water: it is less dense in its solid state than its liquid state . Oceans on some other planets consisting of other types of liquids, such as methane, cannot have icebergs precisely because the frozen substance would sink . </P>

What is the depth of an iceberg below the surface of the sea