Mix water and Crab Boil in large (10 to 12 quart) stockpot. Bring to boil on high heat. Stir in sausage, potatoes, celery, onions and garlic. Return to boil; cover. Boil 15 minutes.
Squeeze juice from lemons into the water and add lemons into the pot. Stir in shrimp. Return to boil; cover. Boil 1 minute.
Turn off heat. Stir in corn. Let stand 5 minutes. Drain well and serve.