In a large skillet or wok heat the 2 tablespoons olive oil; stir-fry Swiss chard over medium-high heat for 2 minutes. Add water and cook 2 minutes more. Add salt and pepper to taste. Remove from heat. In a small bowl combine the 1 tablespoon oil and the vinegar, set aside. To serve, divide chard among the pieces of toast. Drizzle with the oil-and-vinegar mixture. Top with arugula and feta cheese. Serve immediately. Makes 6 side-dish servings.