Add the macaroni, water, butter, sea salt, garlic powder and pepper to the Instant Pot
Turn valve to sealing position, and hit PRESSURE COOK for 4 minutes
Allow pot to come to pressure, and after 4 minutes cook time, do a gradual quick release, hit CANCEL, and open lid when pin drops
Gently stir the macaroni, then gradually stir in the cream
Gradually, stir in the cheeses, about 1 cup at a time, and mix well so that it all blends together
Serve immediately, and top with additional shredded cheese, if desired