1. Combine 1 cup water and sugar in a microwave-safe dish. Microwave at HIGH 2 minutes; cool completely. Place syrup, juice, and next 6 ingredients (through cucumber) in a blender; blend until smooth. Pour mixture into an 11 x 7-inch glass baking dish; cover and freeze 3 hours or until firm, stirring with a fork every 45 minutes. Remove mixture from freezer; scrape entire mixture with a fork until fluffy.
2. Place watermelon cubes in a large bowl. Sprinkle with salt; toss to combine. Let stand 10 minutes. Spoon about 1 1/2 cups watermelon mixture into each of 6 bowls; top each serving with about 1/2 cup granita.