I'm having a bit of trouble with the diplacement working from the ocean flattank_fluid_extended node. I got the volumetric fluid to extend, but getting the displacement effect is giving me some trouble. I'm trying to get the volumetric fluid to follow the extended fluid plane's displacement, but it doesn't seem to follow when I point it to the /obj/flattank_fluid_extended/RENDER vs. the /obj/flattank_fluid/RENDER. What is missing in the extended node that doesn't give the volume the proper displacement? Thanks. This is a bit of a new system, so I'm a bit lost in the woods. The surface is working great, though, and I really love the new system.

I remember encountering the same issue and what I did instead is baking the displaced ocean surface (which also saves a lot of time when rendering with motion blur as Mantra doesn't need to displaced the extended ocean surface every frames).

Obviously baking the displaced geo meant the uniform volume shader will work correctly and if you don't want to go my route, you can duplicate the ocean shader, tweak the diffuse value and apply it to the flattank_interior geo node.

I can't remember if exporting the displacement map from the Ocean Evaluate node helps but it doesn't match the look of the displaced extended ocean which prompted me to figure out a way to bake the displaced extended ocean surface.

Great. Thanks! I was going to try this out to see if it would work in a pinch. I think it would be at least a good start.