For sauce, in a small bowl stir together orange juice, water, sugar, hoisin sauce, vinegar, cornstarch, and pepper. Set aside.
Preheat a wok or large skillet over medium-high heat. Add almonds; stir-fry for 2 to 3 minutes or until golden. Remove almonds from the wok. Let wok cool.
Pour cooking oil into the cooled wok. (Add more oil as necessary during cooking.) Preheat over medium-high heat. Stir-fry ginger in hot oil for 15 seconds. Add onion; stir-fry for 3 to 4 minutes or until crisp-tender. Add plums and cucumber; stir-fry for 2 minutes more. Remove plum mixture from the wok.
Add shrimp to the hot wok. Stir-fry for 2 to 3 minutes or until shrimp turn opaque. Push shrimp from the center of the wok.
Stir sauce. Add sauce to the center of the wok. Cook and stir until thickened and bubbly. Return plum mixture to the wok. Stir all ingredients together to coat with sauce. Cook and stir for 1 to 2 minutes more or until heated through. Serve immediately with hot cooked rice. Sprinkle with toasted almonds. Makes 4 servings.