Place the berries, maple syrup, vanilla, and water in a saucepan. Heat over medium heat. Bring to a low boil, stir occasionally and cook for about 4 to 6 minutes until the blueberries begin to break down, mashing them with a wooden spoon. Cook until they thicken into a sauce.
Remove from the heat. The sauce will thicken even more as it cools. Serve immediately or refrigerate until serving (store up to 1 week refrigerated).