You can't really see what the edge of land is; riverbank or cliff. If it's a cliff I'd add a few holes in the ground or pillars of rock just beyond the edge, so you can actually see the land drop. If it's a riverbank, you need foam!
Breaking up the straight line; use a warp shader.
You mean the foreground correct?... I'd like to do both of those...if it's the distant shore ditto....
You have the project actually Ulco, I harvested it from here and it's is called I think unless I renamed it; for Dune Highland.
The camera is at:
-2940.43, -422.883,-10200.6 Rotation-6, -239.871, 0
Perspective: 66.9 Focal length 27.2004
......but am not sure how.