In a large saucepan, saute garlic in butter. Add scallops and shrimp. Cook until no longer pink. Stir in the milk and parsley. Combine cornstarch and water until smooth; stir into cream mixture. Bring to a boil; cook and stir for 2 minutes.
Add linguine to seafood and cream sauce. Stir and let the sauce thicken more.
Serve with a side vegetable- spinach, broccoli, etc.