Hi cardiff.
You may take a look at the data/Env/EnvColors_xxx.cfg files.
Every section have a value for "UnderwaterUpAlpha" and "UnderwaterDownAlpha".
Up is shallow waters and down is deeper sea I think.
Values from 0 to 1. I.e.: 0.80000 is less visible as 0.20000.
Not shure.
Regards.
Echol
t.