One confirmed cause of pea soup water, the green wall, is old nvidia graphics drivers.
Update them, problem solved.
There are other problems which cause it aswell, but just in case you did not know about that one add it to the knowledgebase
Happened for me on my laptop during the early official patches to the game, after one update it hit my setup and the only way to solve it was update .. Which was a bit of a blow at the time , I was trying to stay with the tailored graphics drivers provided by the laptop company for as long as possible, but as these things go it got to the stage where the laptop company stopped support for my particular laptop, and so I had to go with NVidia Generic laptop setup for my laptop range.
These genric drivers are never going to be as optimal as the dedicated ones .. But if I wanted the latest game patches to work I had to use them.
I went back to the old tailored drivers once just to see if they really could not be used ( after a few more official game patches had been pushed out ) .. No joy, old Nvidia drivers will give me pea soup without fail.
Edit : There were quite a lot of participants in an old BGS forum Technical support topic ( probably circa mid 2012 ) had the same problem until they also upgraded nvidia graphics drivers. So it was not just myself with that particular cause.