Combine water, Old Bay Seasoning, onion, garlic, lemon and bay leaves together in a large stockpot. Bring to a boil, then reduce heat to a simmer. Simmer for 5 minutes.
Add in potatoes and cook for 8 - 10 minutes or until fork tender.
Add in corn, cook an additional 3 minutes.
Add in shrimp and sausage. Cook just until the shrimp is opaque and the sausage is warmed through, about 3 minutes.
Use a slotted spoon to transfer shrimp, sausage and veggies to a platter. Serve with butter and cocktail sauce for dipping.
Notes
You can also add crab legs or steamer clams to this! Add them about the same time that you add the shrimp. If you use the small baby red potatoes you could leave them whole or cut them in half. Nutrition information for estimation purposes only.