I know someone already spotted this but i was unable to find it in the forum !!!
so... if someone has a solution to get rid of this... :-\
(http://i45.servimg.com/u/f45/10/05/42/42/debutr11.jpg)
Is this using a Lake Object or something else? If it's the Lake Object, you might be able to shift the problem to a different direction from the camera where it won't be noticeable, because the Lake Object uses polygons which radiate from its centre. Try moving the lake centre by a few kilometres in one direction. While testing this I would render cropped regions that only show the water near the horizon.
Matt
ok thanks ^^
already 100 hours rendering... so I'll try a different center for the Lake object in a crop render when this one will be over ;D