Poach the Shrimp: In a medium saucepan, bring water to a gentle simmer. Add the shrimp and cook for 2–3 minutes until they turn pink and opaque. Immediately transfer them to an ice bath to stop the cooking process.

Prep the Dressing: In a mixing bowl, combine the mayonnaise, lemon juice, Dijon mustard, dill, salt, and pepper. Taste and adjust the seasoning as needed for a balanced flavor.

Combine Ingredients: Gently fold in the poached shrimp, diced celery, and minced red onion into the dressing. Be careful not to break the shrimp while mixing, ensuring everything is well-coated.

Chill: Cover the bowl and refrigerate for at least 30 minutes before serving. This allows the flavors to meld beautifully together.