The place is just on west bank near village Rab in Vellen. Check attached map.
The water is like pushed back form the lake bank by unknown force, forming like a wave standing still.
Geralt can swim in the empty space, though there is no water graphically there.
Game version 1.12.1.

What's that Diablo III overlay you've got running there? Do you have it always running? Tried disabling it to see if that doesn't help?

I can verify it for the English version. Its west of Drudge.
No mods installed.
stu

http://www.classicshell.net/

Disabling it wont help for that graphical error. Wonder if they fixed it?
It is a srtat menu glitch of taking printscreen screens in Withcher 3 :)

Used to see that sort of thing in Skyrim,didn't worry too much about it as long as I could continue playing.Sometimes reloading game and going back to scene it was back to normal performance/working.