1. Combine 1/2 cup water and sugar in a small saucepan. Bring to a boil, stirring until sugar dissolves. Place pan in a large ice-filled bowl for 25 minutes or until cool, stirring occasionally.
2. Place sugar syrup, melon, and remaining ingredients in a blender; process until smooth. Pour mixture into an 8-inch square glass or ceramic baking dish. Cover and freeze until partially frozen (about 1 hour). Scrape with a fork, crushing any lumps. Freeze, scraping with a fork every hour, 3 hours or until completely frozen.