Newly fallen snow will have soft edges. Ice generally has harder edges. I will leave these hard edges until I paint the "softer" snow in the middle and background, then adjust as needed.
I want the water to be dark, but not as dark as the darks in the background. I made the color more intense to make the water appear to come forward, by using a combination of Phthalocyanine Blue and Manganese Blue. Manganese Blue is the coolest blue.
Ice traps the cool light inside its crystalline structure. If you've seen icebergs in person, you will notice how blue they are.
The balancing act here is to get the "coldness" of the ice, yet also to make this area come forward. The intensity of color should solve that problem.
This step establishes the basic pattern of the light, middle and dark areas of value. Getting that correct is the key to a successful painting.
The next step will concentrate on the still large light area of the snow.