Thaw cod and shrimp, if frozen. Rinse cod and shrimp; pat dry with paper towels. Cut cod into 1-inch pieces. Set cod and shrimp aside.
In a large saucepan or Dutch oven cook and stir sweet pepper, onion, and the 2 cloves garlic in hot oil over medium heat until tender. Stir in tomatoes, the water, salt, and black pepper. Bring to boiling. Stir in cod and shrimp. Return to boiling; reduce heat. Simmer, covered, for 2 to 3 minutes or until cod flakes easily when tested with a fork and shrimp turn opaque.
In a small bowl combine basil, lemon peel, and the 2 cloves garlic. Ladle stew into bowls. Sprinkle with basil mixture.