I don't know if it has any bearing on what you are looking for; however, what you have given, "Normal seawater at 17% salinity, the density is 1025..." sounds quite strange. Where is this "normal", and by any chance to you mean instead a SPECIFIC GRAVITY of 1.025 (that would in my opinion be more "normal", at least for a seawater of say 3.5% or so salinity)?
I lack any seawater data on my computer other than Bowditch. Consider downloading Bowditch and perhaps obtain API RP 45.
Seawater salinity (often measured in parts per thousand) varies in different areas of the oceans. The Red Sea has higher salinity than the Gulf of Mexico. The average may be about 35 parts per thousand. Some polar areas may have warmer water with more salinity that are below the cooler and less saline water. Samples at Milford, CT are around 26 and Woods Hole over 32.