Bring the water to a boil in a large pot. Once boiling, whisk in the seafood boil seasoning. (You can buy a pre-mixed package or make your own).
Return the water to a rapid simmer and add the garlic, sausage, and corn. Return to a simmer, cover with a lid, and cook until the corn is just tender, 8-10 minutes
Add the crawfish and lemon juice, stirring to combine. Cover and simmer until the crawfish turn bright red, 5-7 minutes.
When ready, season to taste with salt and pepper as needed; if the seafood boil is too salty, add water by the cup until you reach your desired seasoning level.