In a medium bowl, whisk the olive oil with the lemon juice and the remaining salt. In two 1-quart glass jars, layer the shrimp, garlic, onion, bay leaves, parsley and 6 of the lemon halves. Add the crab boil seasoning and the lemon dressing and cover. Marinate the shrimp in the fridge for
12 to 24 hours before serving.