This is a nice picture, so what's wrong with it?
I think the problem is
The dark part of the moon is still there - it doesn't become transparent and the stars shouldn't be seen as the moon would block them out.
So it should look like this (courtesy of @Chuck):
There are lots of problems with the image.
1. Red and blue squared stars has been used a couple of times.
2. Yellow part of the sea has been used three times.
3. You cannot have stars inside the moon and the white blue area is added later and there is a clear blur in the photo as shown below.
Beastly's answer does work. Here are some other things I noticed:
- There are three strange spots of luminescence near the horizon on the water
- The edge of the moon is much brighter than the inner parts, whereas the moon tends to be lit with a smoother gradient up to the shadow (see below image, sourced from here)
- The trees seem to be illuminated selectively, in some places but not others
see illuminated tops and bottoms of tall trees but their shadows are totally missing given such separation between those trees.
illumination happens from the other side( on which the moon is located ), the trees also should cast sharp shadows, which are missing.
The 3 patterns of stars immediately above the horizon are of type copy and paste, so not natural!
The other answers taking the image apart in discrete steps are right on the spot. However, having tried to create landscapes in Photoshop countless times, I can tell you I immediately knew this was artificial, even before noticing the three bands in the sea. The lighting, the lack of noise, how the waves don't play with the shore, the impossible exposure (you can't produce such image with a camera), the lack of the DOF...
It's about the holistic approach. All the little things could be overlooked if only the pieces worked together. If you look at the works of the old masters, they are also often "faulty" from up close.