Thaw Shrimp if frozen. In a large skillet cook onion, celery, green peppers and garlic in margarine till tender but not brown. Stir in undrained tomatoes, parsley, salt, paprika, cayenne pepper and bay leaf. Bring to boil reduce heat. Cover and simmer for 15 minutes.
Stir together cold water and cornstarch. Stir cornstarch mixture and shrimp into tomato mixture. Cook and stir till thickened and bubbly. Cook and stir about 2 minutes more or till shrimp turns pink. Remove Bay Leaf. Serve over hot rice.