Frazil ice formation represents the first stage of sea ice growth. The frazil crystals are usually suspended in the top few centimetres of the surface layer of the ocean and give the water an oily appearance. In the open ocean the crystals may form, or be stirred to a depth of several metres by wave-induced turbulence. Frazil ice gives the water an oily appearance. A later stage of freezing than frazil ice when the crystals have coagulated to form a soupy layer on the surface.
Grease ice reflects little light, giving the surface a matt appearance.
Grease ice behaves in a viscous fluid-like manner, and does not form distinct ice floes . 10-15 cm thick. Less elastic than nilas and breaks on swell. Usually rafts under pressure. 15-30 cm thick.