1. Combine cranberries and water in a saucepan. Bring the water to a boil, reduce heat to medium, and cook until all the cranberries have softened and popped, 5 to 7 minutes; remove from heat to cool slightly.
2. Stir sugar and gelatin into the cranberry mixture until dissolved completely. Add pineapple with juice, apples, and walnuts into the cranberry mixture; pour into a 2-quart serving bowl.
3. Cover bowl with plastic wrap and refrigerate until chilled and firm, 3 to 4 hours.