1In Dutch oven, heat 12 cups water and seafood seasoning to boiling. Add shrimp. Cook uncovered 3 to 5 minutes or until shrimp are pink; drain.
2Peel shrimp, leaving tails on 24 shrimp. Make a shallow cut lengthwise down back of each shrimp; wash out vein. Chop remaining shrimp. In large bowl, mix chopped shrimp and remaining ingredients except avocado and cilantro. Cover; refrigerate 2 hours. Chill shrimp with tails separately.
3Evenly divide shrimp salad among 8 footed serving dishes. Garnish with avocado and cilantro. Hang 3 reserved shrimp with tails around rim of each dish to look like claws.