This final is the result of experimenting with placing a large mossy rock in the foreground of the river; a fish jumping out of the water - both surrounded by a vortex shader. Neither of those two tests yielded a pleasing point of interest. I proceeded to pursue a makeover.
Ulco offered a very nice grouping of rocks in rough waters file to try. I placed this additional population of fake stones in the chain hoping it would make an improvement; but, the river looked too busy, especially since either side is heavily populated with vegetation.
I decided to revert to the original river and adjust the two additional suns and enviro-light settings by reducing their strengths. This made a much better scene since now the vegetation appears less saturated; and overall, better contrasts.
Clip files used for the shoreline fake stones are from dandelO; and, vegetation models are by Walli.