Fill a large pot with water and bring it to a boil.
Add salt, Old Bay seasoning, onion, and garlic to the boiling water.
Add the potatoes and cook for 10-15 minutes until tender.
Add the corn and cook for an additional 5 minutes.
Squeeze the lemon halves into the pot and drop them in.
Add the shrimp and cook for 2-3 minutes until they turn pink.
Turn off the heat and let the mixture sit for 5 minutes.
Drain the pot and spread the shrimp and vegetables on a large serving platter.
Sprinkle chopped parsley over the top for garnish.
Serve immediately with extra lemon wedges.