The soft light brings out the intensity of the colors and keeps the reflections softer and more subdued. You'll need your polarizing filter to control glare. Try running a whole series of shutter speeds at one location. You'll be pleasantly surprised at the variety of interesting effects. If you're going to hike in to a special waterfall, ask a ranger when to expect the best light.
Many waterfalls are in deep forests, where they get a lot of shade.
Sometimes midday is the only time they're properly illuminated. Again, play with shutter speeds to create different effects. Because the treetops create a heavy canopy, the deep forest has an environment distinctly its own. It's a world of green, and for us, the more intense and mistier, the better. Textures and colors are intense at midday, when the light is strongest.