The tree with orange outline is the one I drag into scene, it is always OK.
But the tree create with terrain brush, when I drag camera away, It looks like cut by the water.
The tree is not Speed tree and without any LOD, so I guess when the tree is optimized to billboard , it got disorder with the water.
I have try to change the shader of water, any shader that is transparent will cause this problem
It’s happen because transparent shaders don’t take the depth buffer in account, they are drawn by the order of the render queue parameter. You need to change the render queue of the water shader. Anyway, this is a old question and you can find a solution in the first page on google. https://forum.unity3d.com/threads/3-2-water-over-billboard-trees.77544/
