Bring 2 quarts water to a boil in a Dutch oven; add shrimp and Creole seasoning, and boil 2 minutes or just until shrimp turn pink; drain.
Peel shrimp, and devein, if desired.
Place shrimp in a bowl or jar. Top with onion and peppers. Stir together 1 1/2 cups water, vinegar, and salt; pour over peppers. Cover and chill 8 hours. Drain before serving.