Hi Eric & Howie, thanks for your comments and crops.
Eric, your crop addresses the imbalance, but I hate to see that slanting rock go!
The original photo has been cropped top and bottom - overexposed sky & sky reflection in water, but the light area down the middle offends the rule of thirds as Howie points out.
I actually went back later in the day to try again from a different position to improve on it, but you guessed it, that scene was gone. The light wasn't there any more.
Thanks for your input.