Melt butter or margarine in small saucepan, and add carrot, celery and onion.
Saute 2 minutes; cover, and cook 3 minutes.
Add soup and water.
Arrange fillets in greased baking dish; cover with vegetable mixture.
Sprinkle with bread crumbs and cheese.
Bake in hot oven, 425Ã‚Â° F., about 20 minutes for fresh fish and 30 minutes frozen.