The sauteed watercress is also great served with seared steak -- just substitute a big pinch of red-pepper flakes for the ginger and omit the sesame seeds.
In a large nonstick skillet, heat 1 tablespoon oil over medium-high. Add garlic and ginger and cook until garlic is lightly golden, 1 to 2 minutes. Add 1/2 of the watercress and cook until wilted, 1 to 3 minutes; transfer to a bowl. Repeat with 1 tablespoon oil and remaining watercress. Stir in lemon juice and sesame seeds and season with salt and pepper. Wipe skillet clean.
Pat scallops dry with a paper towel; season with salt and pepper. Heat 1 tablespoon oil in skillet over medium-high. Add scallops and cook until browned on one side, about 3 minutes. Turn and cook until opaque throughout, 30 seconds to 1 minute. Serve scallops with watercress.