In a 2-quart pot add 4 cups of water, a pinch of salt, and shells left over from shrimp. Cover and let boil for 20 min. Remove lid and stir. Reduce to medium heat and re-cover. Cook for 20-40 min or until liquid has reduced to two cups. Set aside for use in recipe.
Melt the butter in a large pot over medium heat. Mix in onion and green onions. Cook and stir until tender. Add 1 1/2 of water and creamed corn. Cook 20 minutes still at medium heat, stirring occasionally, until heated through.
Mix in shrimp, crab, and lobster and cook until opaque. Stir in half and half and parsley. Reduce heat to low; continue to cook and stir 15 minutes. Mix in liquid shrimp broth and Creole seasoning; season to taste with salt and pepper.