How to Make It
In a large saucepan, combine the water with a large pinch of salt and bring to a boil. Add the polenta in a thin stream, whisking constantly.
Reduce the heat to low and simmer, stirring constantly with a wooden spoon, until the polenta is thick and the grains are tender, about 20 minutes. Stir in the butter, season the polenta with salt and pepper and keep warm.
In a very large skillet, heat the olive oil until shimmering. Season the shrimp with salt and pepper. Add them to the skillet and cook over high heat until they are lightly browned on one side, about 2 minutes. Add the garlic, turn the shrimp over and cook until cooked through, about 1 minute longer.
Transfer the polenta to shallow bowls. Top with the shrimp and some of the garlic oil from the skillet. Serve right away.