Basically what i did was using psunami i left only the reflection part by doing a linear key of the rest and animating it. Besides I took a part of the footage of my lake and color corrected it properly and use as luma mask for the psunami. It does not look bad, but it is not amazing neither.
If you have already tried to experiment with the different displacement map settings (channels and Luminosity) and are not getting results you could try to duplicate the Water footage (and turn the layer off) and boost up the contrast so the displacement effect is more drastic. If you are still not getting results you could also try applying the turbulent displace effect on your reflection and animate the evolution.