To make the dressing, stir together the yogurt or mayonnaise, sour cream, lime zest and juice, dill, mustard, garlic, and salt. Refrigerate until ready to use.
Cook the Shrimp. Bring a pot of water to a boil. Add the shrimp and cook for 3 minutes, until cooked through and pink.
While the shrimp are cooking, prepare an ice water bath. Remove the shrimp to the ice water bath using a skimmer. Let them cool for 3 minutes, then drain them in a colander. Chop them into bite-sized pieces.
In a mixing bowl, stir together the chopped shrimp, green onion, diced cucumber, and dressing, until creamy. Enjoy!
