Place the arugula and watermelon in a large bowl.
In a small bowl, whisk together the olive oil, lemon juice, salt, and pepper.
Pour enough dressing on the arugula to moisten.
Toss well and place on 6 salad plates.
With a very sharp knife or a vegetable peeler, shave the Parmesan into large shards and sprinkle them on the arugula and watermelon.
Sprinkle with salt and serve.
