Lantiroch with water effects...
One can paint over the water effects which had a calming effect upon my soul. The brown things in front of the horses are not magic horse dung, but small and water-polished rocks.
The green water was added after inspecting what Ted Nasmith had done on his beautiful painting of the scene from the book. I mimicked him by sloppily washing some green waste-water on the horsies and presto: White Water Horses. The word lantiroch is a contraction of two or maybe three Sindarin words, which I cannot remember now, but I found them partially here, Hisweloke's Sindarin - English phrase-/wordbook.
Thanks are going to misters El Zorro and Scott B.! Thank you for the tips on this one!