I was experiencing issues with the OCEAN modifier, and then I tried to render it alone, and the same error occured (only 10.000 faces).
I have seen a tut in which the guy used way higher resolution, and still, it was showing relatively fast and flawlessly in Cycles.
I have 20gb, and the render crashes after ramping-up from 7 to 15gb of full mem usage (still very high for a subdivided plane with a modifier in it).
I have tried to attach the .blend file, but I don't see that option here anymore.
Thank you.