In a large mixing bowl, combine the cooked shrimp, diced cucumber, cherry tomatoes, and red onion.
In a separate bowl, whisk together the mayonnaise, sour cream, lemon juice, garlic powder, dill weed, salt, and pepper until smooth.
Pour the dressing over the shrimp and vegetable mixture. Gently toss until everything is well coated.
Cover the bowl with plastic wrap and refrigerate for at least 30 minutes to allow the flavors to meld.
Before serving, give the salad a gentle stir and adjust seasoning if necessary. Garnish with fresh dill if desired.