Rinse the cleaned octopus under cold water. In a large pot, combine water, celery, lemon, bay leaf, peppercorns, and salt, then bring to a gentle boil. Dip the octopus tentacles into the boiling water a few times until they curl, then reduce the heat and simmer for 40-45 minutes.

While the octopus simmers, prepare another pot of water with lemon juice, tangerine juice, bay leaves, and salt. Bring this mixture to a boil. First, add the squid tubes and tentacles, poaching for about 2 minutes until they turn opaque. Next, add the shrimp and let them cook for another 2 minutes until pink and firm.

In a bowl or jar, combine olive oil, tangerine juice, lemon juice, minced garlic, honey Dijon mustard, and a pinch of salt. Whisk together until emulsified.

In a large mixing bowl, combine the cooled octopus, shrimp, and squid. Pour the dressing over the seafood and gently toss until everything is well coated.

Let the seafood salad rest for a few minutes at room temperature to allow the flavors to meld together. Serve garnished with fresh parsley.