I'm guessing you have a radial light in there judging by the shadow castings. My advice is to stick to just normal sunlight for now to achieve a more natural effect. Something that may help is choosing a different pov more looking up at the structure. If you adjust the document set-up to something more like portrait as opposed to landscape you will still be able to see the water. The main thing with the sky is it does'nt match the colour of the water, it is too purple as opposed to blue. Remember I don't always get the results I want when useing this method, and have scrapped a few pieces of work as a result. Just keep practicing and try out some different skys and blend methods. Morguefile has some excellent royalty free sky photos especially by a photographer called cohdra. Keep at it as this certainly has the potential.

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