Thaw crawfish or shrimp, if frozen. Rinse crawfish or shrimp under cold running water; set aside.
In a 3-quart saucepan cook celery, onion, green pepper, and garlic in margarine or butter about 5 minutes or until tender. Add water, salt, thyme, red pepper, black pepper, and bay leaf. Bring mixture to boiling. Add rice. Reduce heat; cover and simmer for 15 minutes or until rice is tender.
Stir in undrained tomatoes and tomato paste. Add crawfish or shrimp. Cook for 2 to 3 minutes more or until crawfish or shrimp are heated through. Remove bay leaf. Serve in soup bowls. Garnish with celery leaves, if desired. Makes 4 servings.