Sauté bacon in a large pot over medium-high heat until crispy, 3-4 minutes. Remove the bacon from the pot and place on a plate. Drain all but 1 Tbsp bacon grease from the pot. Add diced onions and celery to the bacon grease in the pot. Sauté over medium heat until soft, 3-4 minutes. Add potatoes. Saute 1-2 minutes.
Reduce the heat to low. Add the flour and stir, cooking until the flour is completely moistened.
Add the milk and increase the heat to medium. Heat the chowder until it is steaming, but just before it starts to boil, stirring often. Keep the soup at this point until the potatoes are nearly tender, uncovered, 10 minutes. (Reduce the heat if the milk starts to foam.)
Add the cod, scallops (non smoked!) shrimp, and corn. Add the cooked bacon back to the pot. Continue to heat, just below boiling for an additional 10 minutes, until the fish is cooked through.
Add the parsley, salt, pepper, and smoked scallops. Taste and adjust seasonings as needed. Serve immedietely.