To a medium mixing bowl add the dill, watercress, fennel, scallions, and blood orange segments. Season with salt and pepper, to taste, drizzle with olive oil and add the scallops. Right before you're ready to serve, add the lemon juice. Toss to combine. Arrange scallop shells on a platter and spoon scallop crudo into the shells, garnishing with a little more sea salt and a drizzle of extra dressing. Serve immediately.