1. Rinse fish and pat dry; stuff cavities with thyme, dill, bay leaves, and garlic. Rub outside of fish with olive oil and sprinkle with salt and pepper.
2. Place fish on a grill over a solid bed of medium-hot coals or on a gas grill set at medium-high (you can hold your hand at grill level only 3 to 4 seconds); close lid on gas grill.
3. Cook, turning once with a wide spatula, until fish is opaque but still moist-looking in thickest part (cut to test), 18 to 20 minutes total. Transfer to a serving platter.
4. To assemble each taco, stack 2 tortillas; top with chunks pulled from fish, salsa, lettuce, tomatoes, and cilantro. Squeeze lime over filling, fold tortillas, and eat.