I know Unity Terrain isn’t the most robust thing but has anyone ever seen this issue where a plane (in this case, the water) clips trees/details at certain angles?
I had the same issue with a particle effect that I was able to fix by creating a unique Sorting Layer, but Sorting Layers in 3D...?
Anyway, I have never seen this one before, so hopefully, one of you knows how to fix it.
Is your water transparent?
I had this problem and it was because the water's transparency shader was rendering in front of the detail transparency shader.
I haven't found a solution so far. I just switched my water to an opaque shader...
Try switching your water to opaque. If that fixes the problem than you know it's a problem with the detail/water transparency shader.