I have never really worked with photo manipulations, but I have tried to recreate a design similar to yours with how water reflections typically work.
The image I used were not stocks and this is just an example. >_>
If an object is lying on the surface of the water and actually submerged into the water, the reflection should touch the actual object and overlap depending on how much the object is submerged into it. By the looks of the piano, only the legs are submerged, thus
the reflection's legs should "touch" the location where the legs are fully submerged. Unfortunately, reflections cast by water is different from a mirror's reflection; your reflection is that of a flat 2-D object reflected across an axis. =]
Because of the sky, the sun should either be blocked out by clouds or gone. The reflection should be located directly underneath the piano (this would work out if you make the legs touch).
The most important part is that the keys or any upper side of the piano should
not be seen on the reflected image. Therefore, you shouldn't be able to see the keys and the area with the strings (excuse me since I do not play the piano or know the piano so I don't know the actual name of that part of the piano). Why? Because the water is reflecting the bottom of the piano. There is a possibility that one can see the "stringy area" (brown) of the piano, and that only works if the cover of the piano (or whatever you call that black board you raise up high) is shiny enough to reflect the strings. The water which is reflecting the piano, can reflect the reflected image of the strings and you can see a small portion of it. I know that was confusing. x_x
So here's an example:
The example I show only shows how the reflection works, but only a slight hint of it should show on the water. So my photo manipulation is actually inaccurate but it was just a quick photo manip.

Nothing is reflecting the keys from the top, so again,
you should not be able to see the keys of the piano on it.
The covering of the piano should have a blue hue around the edges because of the colors of the water reflected on it. The same goes with the legs. If possible (and it's hard to imitate), the legs should glisten with waves and specks of blue/white because of the reflection. I couldn't do this well, but hopefully you can!
The legs that are submerged into water--- they gradually disappear. They fade into the water; even though if it is already covered in water, you should still be able to see it as it goes deeper because the ocean in the picture is still.
Last but not least, is the direction of the reflected image (I'm tired of typing that word: reflect. >_> It feels repetitive...) It should be reflected straight down and towards the viewer which is bottom center rather than the bottom right corner. The location of the sun should effect this, but because of the backdrop you have, that's how it should reflect. =] The reflection itself, should be
darker and less
saturated. It shouldn't be solid-- you should be able to see the water's texture on it. For the reflection, I simply used "Soft Light" on the water so the texture seeps through.
As for your actual photo manipulation, perhaps it's just preference, but increasing the contrast of the piano may be a good idea.

It seems as if the lighting for the piano is all over the place (like a studio), and that's a little unrealistic looking compared to how the lighting is outside. The entire piano, since it's black, should reflect the waves of the water too, but just only a little.
=]
I hope this isn't too long, and that you're able to follow it well (and even add more too it).
I'd love to see the outcome!