Well, when i saw the mountain reflections, i immediately hopped over to YouTube to see if i could find a video of Bob Ross doing one of his famous landscapes, but methinks that they have since been removed from the site, such a shame.
Anyway, If you look at some photographs or paintings of reflected mountains, you'll notice that realistically the closer to the horizon they get, the lighter they appear, Usually do to a higher concentration of water vapor across the surface of the water mass. This creates a foggy effect, the closer you get to the horizon line, this happens on both sides of the reflection. In terms of pixel art you might be able to pull this off with dithering, if you won't want to up your color count, however, since you've used a lot of white in the polar bear and ice, you might be able to do it with some white and lighter blues.
Good luck.