Looks pretty good. The way you did the water with the pattern brush and transform tool is something I do too, and it’s a good trick that saves a lot of time.
What is the lighting scheme here? Where is your light source? I don’t see any distinct form or cast shadows to indicate where your light source is, that that flattens out the all the forms. Also, is that a moon/planet in the sky? It’s a bit too vague. Same with the one on the right–is that saturn? If you want this to have a sci-fi feel, you might as well make them more obvious.
The composition feels a bit empty. Wouldn’t some nice clouds make this scene more interesting? Also, the central alignment of the planet/moon with the figure in the middle of the image isn’t very interesting in terms of composition. Try offsetting them for better visual flow/balance.