Smoked Fish Dinner

Name: Smoked Fish Dinner
Ingredients: 2 medium cucumbers (about 1 1/2 pounds), peeled, halved lengthwise, and thinly sliced; 2 tablespoons kosher salt; 1/4 cup sour cream; 3 tablespoons chopped fresh dill; 3 teaspoons white wine vinegar; Pinch cayenne pepper; Freshly ground black pepper; 1/2 red onion, thinly sliced; 1 to 1 1/4 pounds assorted smoked fish, such as salmon, trout, mackerel, or whitefish; 1 bunch watercress, thick stems trimmed; 1/2 cup prepared horseradish; Optional: Multi-grain bread