有關海水密度

The density of surface sea water ranges from about 1.020 to 1.029 g/cm-3, depending on the temperature and salinity.

The average density of sea water at the surface of the ocean is 1.025 g/cm-3; 
sea water is denser than fresh water (which reaches a maximum density of 1.000 g/cm-3 at a temperature of 4°C) because of the added mass of the salts.

According to the information provided by the below website, maximum density of salt water occurs at salinity of 0.025 and at a temperature of  -1.33ºC

For further details, go to this website:

http://www.vub.ac.be/ANCH/educ/Marine%20Physico%20Chemistry%20Pdf%20version%20Chs%201%20to%207/Chapter%202%20Salt%20Temperature%20and%20Density.pdf