Prepare the octopus by rinsing it under cool running water. In a pot, combine water, a chopped celery rib, halved lemon, bay leaf, peppercorns, and salt. Boil, then add the octopus and simmer for 40-45 minutes until tender. Cool and chop into pieces.

In the same pot, bring back to a boil and add halved lemon and tangerine. Poach the squid for 2 minutes. Add peeled and deveined tiger shrimp, cooking for another 2 minutes until bright pink. Drain and cool.

In a mixing bowl, whisk together olive oil, tangerine juice, lemon juice, minced garlic, honey Dijon mustard, and salt. Stir in chopped parsley.

In a serving bowl, combine octopus, shrimp, and squid. Pour dressing over seafood and toss gently to combine.

Chill in the refrigerator for about 30 minutes. Serve cold or at room temperature.