1 (2-pound) piece seedless watermelon, rind removed and flesh cut into 1-inch pieces to yield about 3 1/2 cups
1 (6-ounce) can pineapple juice, chilled
3/4 cup ginger ale, chilled
1/3 cup fresh lime juice (from about 3 large limes)
1/2 cup grenadine (recommended: Rose's)
The ginger ale can be replaced with dark rum.