The tip of an iceberg which is visible above the waterline is usually only about 1/7 or 1/8 of the mass of an iceberg.
Seawater is slightly denser than ice and this means that the iceberg floats with most of its mass below the surface. In comparison a cork, which has a density of about 20% that of water, floats close to the water surface. Ice has about 90% of the density of water but the density of seawater is also influenced by the temperature and salinity.
