Combine the rolled oats and water in a large bowl. Cover the bowl and refrigerate overnight to allow the oats to soften.
The following morning, drain any excess liquid from the soaked oats using a fine-mesh sieve. Reserve about ¼ cup of the drained liquid.
Dice half of the apple into small, uniform pieces and set aside. Roughly chop the remaining half of the apple.
Transfer the drained oats, roughly chopped apple, pitted dates, maple syrup, ground cinnamon, ground ginger, vanilla extract, and almond milk to a blender or food processor.
Blend the mixture on a medium setting until it achieves a thick, creamy consistency with some small date and apple pieces remaining. If the mixture is too thick, add a tablespoon or two of the reserved soaking liquid until desired texture is reached.
Spoon the blended oat mixture into individual serving bowls. Stir in the reserved diced apple.
Garnish each serving with chopped walnuts and shredded coconut before enjoying.