Tomato and Watermelon Gazpacho

4 medium tomatoes, preferably heirloom varieties, chopped

4 cups diced seedless watermelon

1 cucumber, peeled, seeded and chopped

1 yellow bell pepper, chopped

1 medium shallot, sliced

1/3 cup loosely packed basil and mint, plus small leaves for topping

Kosher salt and freshly ground pepper

1/3 cup extra-virgin olive oil, plus more for drizzling

3 tablespoons champagne vinegar