In a mixing bowl, combine the watermelon, tomatoes, mozzarella, basil, and vinegar. Toss well.
Season with salt and pepper if desired to taste (note that mozzarella is naturally salty, so you may not need any seasoning depending on preferences). Enjoy!
Notes
This makes one large serving (for a hearty snack) or two smaller servings (for a side dish to a meal). The nutrition analysis below assumes one large serving.
Nutrition (approximate for the entire recipe, assumes dash of salt): 209 calories, 8 g fat, 440 mg sodium, 23.5 g carbohydrate, 3 g fiber, 17.5 g sugar, 0 g added sugar, 11.5 g protein, Vitamin D: 1%, Calcium: 25%, Iron: 6%, Potassium: 15%