First time I've successfully do this simple trick in Photoshop. But first up you need to have a good shot in the first place before you're using Photoshop to make it surreal to your taste of course. Okay let's talk about how I do this if you want to do this yourself. Go ahead and do it. I have learnt this trick from Scott Kelby.
1) Select the skyline.
2) Control J or Command J. (That's make a copy in a new layer)
3) Control T or Command T. Using the free transform tool and flip it upside down. You nearly there.
4) Using motion blur in the effect filter. I select about 25 pixels for this blur that it's up to you how much you want it. Need to also adjust the angle of the blur to imitate water or true reflection.
5) (Optional) If you using a wide angle lens try to adjust the buildings perspective with select the building and free transform tool to straighten the buildings. Need to mask out some area when you done.
6) (Optional) If you could lower the exposure of the water reflection just a touch that's really sell the fake as well.
7) Congratulations you're done.You now create a fake reflection shot in your photo. This is simple yet powerful tool in Photoshop that you could use to enhance or expand your vision.
If you find this tips and tricks useful, let me know in the comment below. I love to hear what you have done with it and share the shots with me as well.