Drain mushrooms, reserving liquid; set aside. Melt butter over medium-high heat in a large skillet. Add celery and onion; saute for 4 minutes or until soft.
Remove from heat and stir in 1/2 cup dressing, water and reserved mushroom liquid. Stir in stuffing mix and cranberries until thoroughly moistened. Combine turkey, mushrooms and remaining 3/4 cup dressing in a seperate bowl.
Spread turkey mixture evenly in a greased 8 inch baking dish. Top with stuffing mixture. Bake at 350 for 40 minutes or until bubbly and brown.