Textures for Aprons / Poligons over deep water do not show at all

When I try to place any material / texture on an apron or polygon over open water - nothing is showing. It seems like it becomes slightly brighter, but no image showing. I tried several default materials - it stays transparent.

Does anyone know what’s the issue with that? I want to place a foaming water trail next to a static cruise ship model. But neither custom or default aircraft_carrier AC_streamwater material do not show at all…

What’s going on with that?