Rename background layer to unlock it.
Duplicate background layer.
On the top layer, select the pool with the polygon lasso tool. Feather selection a couple of pixels. Then delete the selection to reveal the bottom layer image.
Make the bottom image active and Select All. Edit>Transform>flip vertical. Move bottom layer until the image falls into positon as reflection inside the selected cut out.
Use Filter >Distort >Ripple, followed by slight Filter >Blur >motion blur.
Use adjustment layers on the bottom layer to darken the "water" slightly and give a little color cast.
Adjust color on the entire image to reduce the strong redish lighting.
Make a little perspective correction to square up the buildings.




original image by ABV