In a saucepan of boiling salted water, cook the calamari and shrimp for 3 minutes, or just until opaque and tender. Drain and pat dry.
In a large bowl, combine the calamari, shrimp, scungili, celery, garlic, olives, and salt and pepper. Chill the mixture, covered, until ready to serve.
In a small bowl, whisk the lemon juice, oil, salt, and pepper together. Add the dressing to the seafood mixture along with the parsley and toss to combine.