I like the color of sky and water but the city is washed out. If you had waited for the sun to go down further, you would have had fabulous City lights making the buildings stand out. I think this is what you were trying for but you caught it a little to soon. The horizon line is almost in the center. It should have been further up to be 1/3rd. Funny thing, Since the sky and water are nearly eventless, I think a centered horizon would probably work best in this case, though not the criteria for this challenge. LOL Very good attempt. Try it again if you get the chance.
The skyline seems too small (like a snapshot). Maybe a tighter crop would highlight the skyline more toward the bottom of the frame. Or, when shot, include more sky which would emphasize the height of the buildings more?