Why I can't catch the water in Default Layer with Collision Mask？

[Leon]

 As shown in the following figure，the lake_38_01 in Layer Default,the  Banian rule with 0 submask，only one  collision mask setting in Spawner.

[Peter]

Hi @Leon, the layer-based collision mask works by rendering an overhead image of the scene in orthographic perspective, everything it renders on the given layers (besides the terrain) should be captured for the mask. Can you please check if the water shader still renders when you switch the scene view into orthographic mode? (Click on "Persp" in the top right in the scene view under the compass)
If the water does not render in orthographic, this is most likely the issue. What you could do then as a workaround is to duplicate the water object and apply a "regular" material to it just for the purpose of spawning. You can then later deactivate  that game object when done with spawning for the moment, and delete it completely when the terrain is finalized.
 

[Leon]

Nice method, really helpful!