You've gotten some good advice above. One thing that I would be interested in seeing is the color version, possibly cropped as suggested.
Here is the color image with a quick crop, I didn't really like how it came out in color too much-this is unedited.
This is the crop I had in mind, and it definitely directs the viewer's attention more clearly towards the horizon and sky.
I think the same techniques as Gary mentioned could brighten this color version up as well. I generally prefer the more subtle colors that you captured here to the oversaturated treatment that many sunset images get, so I would try to keep those gentle colors. You could, however, make them more dramatic with some contrast and selective dodging and burning. The rocks play a big part in breaking up the super smoothness of the image, so perhaps there's also a way to play those up a bit.