This is a beautiful scene! I might sugest adding some more contrast to this image, and perhaps playing around with the colors a bit... just to make it more interesting. Good composition though, and nice shot! :)
Perhaps this was a cloudy day, which is an excellent day for a picture like this, and as far as the image is concerned, a great image... But I can't tell if there was any backlighting at all in this image.
Like the title but as far as conveying the challenge, I'm having a bit of trouble seeing it. Might have helped if you included your light source or some forward facing shadows maybe