A simple question, why would you want to freeze the skybox? The skybox is already ‘freezed’ (kind of) by default. And then for your commented line, the answer is simple: There is no other ground, your ground is your watermesh, so you cannot push it to the render list of your water material (you cannot add self).
I don’t want to freeze the sky box, because my scene has a lot of mesh, so I need to use scene freezing to improve performance;
You can do it at scene level, as in your example, or at meshes level -
unfreeze when needed
If there are any moving meshes in our scene the second way is much more convenient because you have full control.
Thank you for your attention, but it doesn’t seem to solve the problem.
So what is the problem, by the way? - https://www.babylonjs-playground.com/#1DFTDT#53
There was a problem with the reflection of the water. and the sky box was cut in half.