Combine the mayonnaise, onion, lemon juice, mustard, and water together in a small nonmetallic bowl and whisk gently.
Season the dressing mixture with salt and pepper to taste.
Cover with plastic wrap and let it chill until you are ready to serve.
If you are using fresh cooked shrimp, pull off the heads and peel the shell off. Remove and discard the dark vein and discard. Rinse and pat dry with paper towels.
Arrange the salad greens on a large serving platter or on individual salad plates. Top with the shrimp and top with tomato wedges and olives.
Serve cold with the turmeric dressing.