This is a nice find and a good time to break the rule of thirds (with the tree; it might have looked better with a bit less water). I like the darker mood (even if it was accidental), but would've liked to see more contrast in the sky. As well, this might have been a bit more emotional as a black and white image.
Overall, a pretty good score for this shot. You said you were unsatisfied with the level of light; perhaps you would've been happier with a re-shoot at an earlier time. A lower ISO would have given you more latitude during your adjustments.
Great subject and I like the viewpoint you've offered. This image is VERY dark though - which although makes it moody and interesting, also means details are lost - I'd have tried to lighten it with shadows/highlights (if you use photoshop), or perhaps Contrast/Brightness.
Colors are pretty, but could be saturated more for a better effect.Sea blends right into the sky, the horizon is right in the middle. Try to use the rule of thirds in both the sky/water and your subject.