A large iceberg floats roughly 90% submerged, bobbing on an animated ocean and occasionally calving chunks with a splash. Ice is only slightly less dense than seawater, so by Archimedes' principle it must displace a volume of water equal to its own weight, leaving just a thin sliver above the surface. Calving happens when thermal stress and wave action fracture weakened ice, sending a chunk crashing into the sea and settling to its own buoyant equilibrium.