Improve the composition a little bit, it’s very rare to have such a bit part of the image out of focus near the center of the image.
Improve shadows, it’s hard to believe that the same light is casting that soft shadow on the wall and sharp shadows under the bridge.
Make the background less blurry.
Add something of known size into the image as a reference point for the rest of the scene, are we looking at a very small bridge or huge rocks?
Water could use some more realistic ripples.
Sun this low usually has a warmer color.
Try using a camera setup closer to real one, I’ll send you a blend file.
Think a little bit about the scene you want to make and the story you want it to tell.
I hope this helps.
Other than that I like the idea and think you will get a great environment in the end.