Thaw scallops, if frozen. Cut any large scallops in half.
Cook spinach according to package directions; drain well. Keep warm.
Meanwhile, in a medium skillet combine water, wine, salt, tarragon, pepper, and garlic. Bring to boiling; add scallops. Cover and simmer for 1 to 2 minutes or until scallops are opaque. Remove scallops from skillet with a slotted spoon.
In a small bowl combine milk and flour. Stir into liquid in skillet. Cook and stir until thickened and bubbly. Cook and stir for 1 minute more.
Stir Parmesan cheese into mixture in the skillet. Return scallops to skillet; heat through. Serve scallop mixture over spinach. Makes 2 servings.