**Prepare the Seafood**:
- For the shrimp: Bring a large pot of salted water to a boil. Add the shrimp and cook for about 2-3 minutes, or until they turn pink and opaque. Remove from heat, drain, and immediately transfer to an ice bath to stop the cooking process. Once cooled, drain and pat dry.
- For the mussels: In a separate pot, bring water to a boil. Add the cleaned mussels and cover. Steam for about 5-7 minutes, or until the mussels open. Discard any that remain closed. Let cool slightly and remove from shells if desired.
- For the scallops (if using): Sear them in a hot skillet with a little olive oil for about 2-3 minutes on each side until golden brown. Remove from heat and let cool.
**Make the Cocktail Sauce**:
- In a bowl, combine the ketchup, horseradish, Worcestershire sauce, lemon juice, salt, and pepper. Mix well and adjust seasoning to taste. If you like it spicy, add a few dashes of hot sauce.
**Assemble the Platter**:
- On a large serving platter or board, arrange the seafood artistically. Place the shrimp, crab meat, mussels, and scallops in separate sections or clusters.
- Add lemon wedges and sprinkle with fresh parsley or dill for garnish.
- Serve the cocktail sauce in a small bowl in the center or alongside the seafood.
**Serve**:
- Serve the seafood cocktail platter chilled or at room temperature. Enjoy with additional lemon wedges and cocktail sauce for dipping.