The crop version is definately an improvement. The original places the castle slightly off centre on both H and V axes. When I saw the original I felt it needed to be more panoramic - less water and sky with more emphasis on the water stretching out. The crop has achieved this to a degree, although I feel it could still improve.
I actually think the cropped version has lost something the original had. It is more grainy now, which I think is a backward step. The original had a hint of an ethereal and a slight mystical feel, which the strange grey area was part of. It is smoother and lighter. That it makes you wonder if it is real I see as an advantage that you should play with and explore. I wouldn't treat it as an obstacle.
I also wonder if you could attempt to get a little more detail on the castle walls. If you have a tripod and don't mind using photoshop and don't consider it "cheating" then I wonder what you could do if you took two images and exposed one for the castle itself, to get a little more detail.
I think another interesting exercise here would be to try different focal lengths, if it is at all possible. With the tele you get the flattening of perspective which I think is possibly going to work best with the mystical feeling with regard to the relationship with the mountains behind. If you can get in with a wider angle, that could also be interesting to see the change. I wonder if this would perhaps appear more real, although perhaps also less interesting.
I think you could also have some fun with a polariser if you have one. The water could take on a different quality, and you could experiment a little with how bold you want the castle to be against the sky.
Many thanks for your comment. I will try blending a different exposure. Trying with different focal lengths, polarizer etc. is quite difficult, since we have no more than one or two days a year with air clear enough to see the mountains from this perspective.
Anyway I will wait and try again