1. Preheat oven to 400° F.
2. Cut squash in half. Remove seeds. Place cut side down on baking sheet sprayed with vegetable pan spray.
3. Combine apples, celery, and onion. Add margarine and water. Put in small baking dish. Cover.
4. Bake squash and apple stuffing for 45 minutes or until tender. Remove from oven.
5. Salt squash. Fill with apple mixture.