In a large bowl, combine the watermelon cubes, diced cucumber, sliced red onion, chopped mint leaves, and torn basil leaves.
If using, sprinkle the crumbled vegan feta cheese over the salad.
In a small bowl, whisk together the lime juice, extra-virgin olive oil, salt, and pepper.
Drizzle the dressing over the watermelon mixture and gently toss to combine, ensuring all the ingredients are coated evenly.
Taste the salad and adjust the seasoning, if needed.
Let the salad sit in the refrigerator for about 15 minutes to allow the flavors to meld together.
Once chilled, give the salad a final toss and transfer it to a serving dish.
Garnish with additional mint and basil leaves if desired.
Serve the watermelon salad chilled and enjoy as a refreshing side dish or a light summer appetizer.