1 3/4 large cucumbers, peeled, seeded, and coarsely chopped (about 3 1/4 cup), plus 1/4 large cucumber, peeled, seeded, and cut into small dice for garnish (about 1/4 cup)
2 scallions (white and green parts), coarsely chopped
1/2 cup (loosely packed) assorted fresh herbs, such as basil, chives, and mint, coarsely chopped, plus ¼ cup finely chopped (for garnish)
1 (1/2-inch) piece fresh ginger, coarsely chopped
1 small clove garlic, coarsely chopped
3 tablespoons extra-virgin olive oil
1/4 cup plain low-fat yogurt
3/4 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
1/4 teaspoon hot sauce
1/4 pound large shrimp (31 to 40 count per pound) peeled, cooked, and cut into medium dice (about 8 shrimp)
1/2 cup seedless watermelon or cantaloupe, cut into small dice