Seawatter or saut watter is watter frae a sea or ocean. On average, seawater in the warld's oceans haes a salinity o aboot 3.5% (35 g/L, or 599 mM). This means that every kilogram (roughly ane litre bi volume) o seawatter has approximately 35 grams (1.2 oz) o dissolved sauts (predominantly sodium (Na+
) an chloride (Cl−
) ions). Average density at the surface is 1.025 g/ml. Seawatter is denser nor baith fresh watter an pure watter (density 1.0 g/ml @ 4 °C (39 °F)) acause the dissolved sauts add mass wioot contributin signeeficantly tae the volume. The freezing pynt o seawatter decreases as saut concentration increases. At typical salinity it freezes at aboot −2 °C (28 °F). The cauldest seawatter ever recorded (in a liquid state) wis in 2010, in a stream unner an Antarctic glacier, an measured −2.6 °C (27.3 °F).