Using a large bowl, add the cut watermelon and set aside for 20 minutes. Then discard the extra liquid that's sitting at the bottom of the bowl. Add blueberries, cucumbers, chopped mint and basil. Set aside.
Whisk together the vinaigrette in measuring cup or small bowl, olive oil, balsamic vinegar, lime, salt and pepper. Drizzle half the vinaigrette over the watermelon, blueberries and cucumbers and gently coat. Transfer to serving dish or platter. Set aside.
Optional: to add halloumi cheese, preheat the grill and spray or coat with oil. Brush the halloumi with olive oil, then add to the grill and leave for 4-5 minutes on each side. Carefully remove and once cooled, cut into bite size pieces.
Drizzle the remaining half the vinaigrette to the salad, add the cut halloumi and crumble feta cheese. Garnish with mint and basil leaves. Serve with grilled meat, poultry, or fish. Enjoy!