In a medium saucepan add Sweet Soy Sauce, garlic and ginger. Dissolve cornstarch in the water; add to the saucepan. Cook the sauce over medium heat for 5 minutes, stirring occasionally. Remove from heat and let cool. Reserve 1/3 cup marinade. Marinate the salmon for at least 30 minutes. Grill or Bake until done. Brush with reserved marinade.