Bring 3 cups of water and a large pinch of salt to a boil. Add the corn grits, reduce heat, and simmer for 10-15 minutes, stirring often, until done. Add more water, ½ cup at a time, to reach a smoother consistency, if needed.

In a medium bowl, toss the shrimp with taco seasoning, salt, and pepper, to taste. Set aside to marinate for 20-30 minutes.

In a large skillet, heat 2 tablespoons of olive oil over medium-high heat; arrange the shrimp in a single layer and cook for 2 minutes. Add the garlic to the pan and flip the shrimp over. Cook for 2 more minutes. Remove from pan.

Serve the shrimp doused with lime juice over polenta. Garnish with cilantro, if desired.