Put the bags of seasoning mix, the water, potatoes, onions, lemons, 1 1/4 cups of the salt, 1/4 cup of the cayenne, and the garlic in a large stockpot. Bring to a boil, cover, and boil for 15 minutes.
Add the sausage, corn, and crawfish or crabs. Using a long-handled spoon, stir around and press the contents of the pot down well into the water. Cover the pot and return to a boil. Boil for 2 minutes.
Turn off the heat. Add the remaining 1 tablespoon salt and 1 tablespoon cayenne.
Using the long-handled spoon, push down the contents in the pot. Cover and let stand for 15 minutes. Drain.
Divide the potatoes, onions, corn, and sausage into equal portions and serve with the seafood on large platters or trays.
Yield: 4 to 6 servings