In a nonstick skillet, combine 4 tablespoons water, wine or broth, garlic, salt, tarragon and pepper. Bring to a boil; add scallops. Reduce heat; cover and simmer for 2-3 minutes or until scallops are opaque. Remove with a slotted spoon and set aside.
In a small bowl, combine flour and milk until smooth; stir into pan juices. Bring to a boil; cook and stir for 1-2 minutes or until thickened. Reduce heat; stir in Parmesan cheese.
Return scallops to the pan; cook for 1-2 minutes or until heated through. Meanwhile, place the spinach and remaining water in a microwave-safe dish; cook on high for 1-1/2 to 2 minutes or until slightly wilted. Drain well. Serve scallop mixture over warm spinach.