Thaw shark and shrimp, if frozen. Cut shark into 1-inch cubes. Discard any skin and bones. In a bowl stir together shark, shrimp, soy sauce, sherry, ginger, and sugar. Cover and refrigerate for 30 minutes. Drain shark and shrimp, reserving marinade. Set aside.
Pour cooking oil into a wok or large skillet. (Add more oil as necessary during cooking.) Preheat over medium-high heat. Stir-fry garlic in hot oil for 15 seconds. Add broccoli; stir-fry for 3 minutes. Add sweet pepper; stir-fry for 1 minute more or until vegetables are crisp-tender. Remove vegetables from the wok.
Add half of the shark and half of the shrimp to the hot wok. Stir-fry for 3 to 6 minutes or until shark flakes easily, being careful not to break up pieces. Remove shark and shrimp from the wok. Repeat with remaining shark and shrimp. Return all shark and shrimp to the wok. Push shark and shrimp from the center of the wok.
Stir reserved marinade. Add marinade to the center of the wok. Cook and stir until bubbly. Return cooked vegetables to the wok. Gently stir all ingredients together to coat with marinade. Cook and stir for 1 to 2 minutes more or until heated through. Serve immediately over hot cooked noodles. Makes 4 servings.