To a large pot or dutch oven, add water, lemon wedges (one lemon), onion, garlic, old bay seasoning. Give the mixture a quick stir, bring to a boil over medium-high heat and add the potatoes. Season with salt and cook the potatoes for 10-12 minutes or until they’re almost done.
Add the corn ears and sausage, and cook for 4-5 more minutes. Remove the dutch oven from heat.
Add the raw shrimp, and cook for 1-2 minutes or until it’s opaque. Be very careful not too overcook the shrimp. Drain the mixture immediately (reserving ½ cup of the broth for serving).
Place all of the ingredients on a platter or sheet pan, drizzle with melted butter (and some of the reserved broth if desired), lemon juice, sprinkle with additional Old Bay seasoning, ground black pepper, and garnish with chopped parsley.