In a large pot, combine the garlic cloves with the coriander and fennel seeds, crushed red pepper, salt, and water. Using a vegetable peeler, remove the zest from the lemon and add to the pot. Halve the lemon, squeeze it into the pot and add the halves. Bring the liquid to a boil and then simmer over low heat for 15 minutes. Add the shrimp and scallops and simmer just until white throughout, about 5 minutes. Drain the shrimp and scallops well and transfer them to a large plate. Leave the aromatics on the seafood. Cover and refrigerate the seafood until chilled, at least 4 hours or overnight.

In a small bowl, whisk the chile sauce with the prepared horseradish, smoked paprika, and the 2 tablespoons of lemon juice. Spoon the smoky cocktail sauce into a small serving bowl.

Pick any aromatics off the shrimp and scallops and arrange the seafood on the platter or in individual glasses with the crab claws. Serve with the cocktail sauce.

The sauce, cooked shrimp and scallops can be refrigerated separately overnight. The cracked crab claws can be covered and refrigerated overnight.

If you can't get cracked stone-crab claws, you will need to crack them yourself. Working with one crab claw at a time, wrap it in a kitchen towel. Working carefully, lightly crack the crab claw with the back of a knife or a mallet to expose as much of the meat as possible, leaving the pincers attached.