Copied sky , pasted to a new layer, curved all the way to the to the right (darker)
then, multiplied, then made an other layer from that.
Then made a 3rd layer, turned vertically for the water reflection.
All 3 layers are multiplied.
A bit of cleaning up with the eraser.
Blurring tool for the sky..
Combined the layers and gave a bit of a curve for some contrast