PPT Slide
Ripples will alternately reflect what's on shore and what's in the sky because they're reflecting on different angles, or look dark and light because from one angle you're seeing through it into the murky brownish lake water and the other you get bright blue or pale gray sky.
Look at real water and sketch ripples. Sometimes in scenic landscapes, the reflections are broken up by a sky-colored streaky mass of ripples that go in other directions and reflect the sky. Putting that in makes it look even more realistic than just drawing the reflections.