By pure luck, I think I've stumbled across the cause: it's to do with *tessellation*. If you disable it completely (needs a P3D restart) you'll find that the water goes back to "normal".Adam, I have the same problem. You described it perfectly. From a distance the water has the appropriate color. As you become more vertical, the water turns completely black. I also have tried all the fixes including REX etc. Has anyone any ideas how to change this or are we stuck with black water?
However - the water quality slider becomes non-operational and you'll get frequent runtime errors. In fact - I found any setting of less than maximum tessellation could produce these errors.
It may be driver and/or GPU related. I have the latest nVidia drivers and a GTX580 - and run with DSR set at 2x.
Adam.