Cut the onion, celery, parsley, and basil.
In a large pot of salted boiling water, cook the tortellini according to package directions. Transfer the cooked tortellini to a colander and rinse under cold water to cool.
In a small bowl, whisk together the olive oil, minced garlic, red wine vinegar, water, lemon juice, salt, and black pepper.
In a large bowl, mix the chopped onion, celery, olives, parsley, and basil. Pour the dressing over the mixture and mix well. Add the shrimp and tortellini, then mix in the remaining ingredients. Adjust salt and pepper to taste.
Chill the salad in the refrigerator before serving.