2Place berries into a blender with water, sugar, lemon juice, balsamic vinegar, and salt. Pulse several times to get the mixture moving, then blend until smooth, about 1 minute. Pour into a large baking dish; the mixture should only be about 3/8 inch deep in the dish.
3Place the uncovered dish into the freezer until the mixture barely begins to freeze around the edges, about 45 minutes, it will still be slushy in the center.