No time for skewers? Gently toss the ingredients in a salad bowl, or dice the tomato, watermelon, and cheese into small cubes to serve as a fresh relish for grilled meats.
Gently toss together tomatoes and next 7 ingredients in a large bowl. Cover and chill 30 minutes to 1 hour. Thread 1 tomato piece, 1 watermelon cube, and 1 feta cube onto a skewer, and place in a serving bowl. Repeat with remaining skewers. Drizzle with remaining marinade, and serve immediately.