Thaw shrimp, if frozen. Peel and devein shrimp, leaving tails intact if desired. Rinse shrimp; pat dry.
Chop 1 Tbsp. of the dark green tops of onions for garnish. Cut pale green and white parts into 2-inch pieces.
In a wok or 12-inch skillet heat oil over medium-high heat. Add ginger; cook and stir 30 seconds.
Add scallion pieces and snap peas; cook and stir 1 to 2 minutes. Add shrimp, noodles, and pineapple; cook and stir just until shrimp are opaque. Add teriyaki sauce and therefore the water; toss to coat. Sprinkle with peanuts and scallion tops.