Season shrimp generously with salt and pepper. In a large skillet over medium-high, heat 1 tablespoon oil. Add shrimp; cook until opaque throughout, turning occasionally, 2 to 3 minutes. Transfer to a bowl; set aside.
Reduce heat to medium. Add remaining tablespoon oil to pan; cook garlic and red-pepper flakes until fragrant, about 1 minute. Add tomatoes and their juice along with 2 cups water; bring to a boil. Reduce heat; simmer, stirring occasionally, until tomatoes have broken down and become saucy, about 15 minutes.