Thaw fish, if frozen. Cut fish into 1-inch pieces. Set aside. In a Dutch oven cook salt pork or bacon slowly until golden brown. Drain, reserving 1 tablespoon drippings in pan; set salt pork or bacon aside.
Add onion to pan; cook until tender. Stir in potatoes, water, salt, and pepper. Bring to boiling; reduce heat. Simmer, covered, about 15 minutes or until potatoes are tender. Add fish. Simmer, covered, about 3 minutes or until fish just flakes when tested with a fork.
Combine milk and evaporated milk. Slowly stir milk mixture into flour until smooth; add to fish mixture. Cook and stir until thickened and bubbly. Add cooked salt pork or bacon; heat through. Makes 6 servings.