Since this was not listed under “known issues” of the changelog I asked the support team about it. The answer was: “DCS World has added new clouds, improved graphical effects and much more,
therefore DCS requires more powerful hardware. […] You cannot revert the water display to the previous version[…]“
Really hope it gets sorted out, since I am not in the position, now should i have to buy a new PC. The performance be optimized with time (take X-Plane as a role model), not worse in my opinion -> so people loose the ability to play the game they paid for.
Reinstalled completely and no optimization tips helped unfortunately.