Soak shrimp in salty cold water for 20 minutes and rinse thoroughly. Pat the shrimp dry with paper towels. Deep-fry the shrimp at 375 degrees for only 20 seconds, then drain. While the shrimp are deep-frying, coat the wok with oil and saute the scallions, garlic and ginger. Add the fried shrimp then season with salt and pepper. Stir-fry for 20 seconds and serve immediately.