[HELP ]Under /above water split view with displacement in orthographic view

I want to fill the space below my water plane with a blue color, like this:



How it should look like:

I tried doing that with post processing, but I stumbled across some problems.




My waterplane has a displacement:

I found a [solution][3] in a unreal forum post, but I can not figure out how to reconstruct it for my displacement.

I recreated another [solution][4]. This one works in 3D View (without the displacement), but not in orthographic.

Anyone any idea how to solve this?