Bring an extra-large pot fitted with a basket strainer and filled about halfway with water to a rolling boil. Add the seasoning mix and stir to combine, return to a rolling boil.

Squeeze the grapefruit halves into the water then add them to the pot along with the potatoes, onion, and corn and cook for 5 minutes.

Next, gently add the crawfish and cover the pot. Depending on the size of the pot, this may have to be done in batches.

Cook for 5 minutes then remove the pot from the heat and let sit for 15 minutes so the crawfish absorb the flavor of the spices.

Lift the strainer and pour the cooked crawfish out on a newspaper-lined table outside.