1. Combine first 6 ingredients in a small bowl. Add 1/8 teaspoon salt and 1/8 teaspoon pepper; stir well with a whisk. Add the satsuma orange sections. Let stand 30 minutes.
2. Heat a cast-iron skillet over medium-high heat. Coat pan with cooking spray. Add scallops to pan; cook 2 minutes or until browned. Turn scallops over. Sprinkle with remaining 1/4 teaspoon salt and remaining 1/4 teaspoon pepper; cook 2 minutes or until done.
3. Place 1/3 cup watercress on each of 4 plates. Arrange 3 scallops on each serving; top each serving with 2 tablespoons salsa. Garnish with orange wedges, if desired.