Here is my best shot: It is a nice picture, but what keeps it from being a great picture is that there is no "there" there. I am not really sure what the subject matter is, the story that is being told.
And it is tough, because with distant subject matter you don't really have a lot of choice. It's "picture" or "no picture." So what to do? First, have a look at what makes the picture interesting. For me it is the pre-Raphaelite look to the clouds, the late-afternoon, directional quality to the light, the contrast between the implied power in the cloud-bank and the fragility or the recreational quality of the sail boats. I would want to see more of the boats and less of the water. When you know what your subject matter is, you can isolate it more effectively and better evoke an emotion in a viewer for whom it is the only impression he will ever have of a scene, rather than a memento of a pleasant afternoon. If I mentally crop the image to isolate only the boat on the left-hand side of the frame, I get more of the look I'd want.
Not meant to be harsh, and hope this helps.
Ben