In a medium bowl, toss shrimp with Old Bay seasoning. Set aside.
Bring 3 cups water and the salt to a boil in a large, lidded saucepan. Gradually stir in grits and reduce heat to medium. Partially cover and cook, stirring occasionally, 10 minutes.
Meanwhile, heat a large stainless steel skillet over medium-high heat. Add bacon and cook until just crisp, about 6 minutes. Remove bacon with a slotted spoon to drain on paper towels.
Reduce heat under skillet to medium and add garlic. Cook 30 seconds to a minute. Add shrimp and cook 3 minutes, turning, until pink. Remove shrimp and garlic to a bowl with a slotted spoon. Stir creamed corn into grits. Reduce heat to medium-low, cover and cook 5 minutes. Let stand 5 minutes.
Pour heavy cream into skillet, scraping up any browned bits from bottom of pan. Simmer 4 minutes until slightly thickened. Stir in shrimp and garlic and bacon pieces. Cook 1 minute.
Pour grits onto platter. Top with shrimp mixture and scatter scallions over top.