It has roughly 2/3 the salt content of regular seawater. Ocean salinity (expressed in-per mil) is approximately equal to the weight, in grams, of salts dissolved in 1000g of seawater. This would be the salt concentration in parts-per-thousand ().Average ocean water has a salinity of 35g of dissolved salts.t has roughly 2/3 the salt content of regular seawater. Ocean salinity (expressed in-per mil) is approximately equal to the weight, in grams, of salts dissolved in 1000g of seawater. This would be the salt concentration in parts-per-thousand ().