When we visited Beauty Creek at Jasper National Park in Canada, we got lots of chances to photograph stunning reflections. The clouds were breaking up fast, and I took several shots with different compositions to include reflections.
This is a manually blended image. I used our iHDR workflow and a 3-stop, hard GND filter. I tilted the filter slightly so that it was aligned with the angle of the mountains. Because I wanted to see the reflections of the clouds, I did not use a circular polarizer. I adjusted the overall exposure so that I could see the details in every part of the image. If you look closely, you can see under the water and the reflections at the same time.