Combine all ingredients in a saucepan, and bring to a boil over medium-high heat.
Cook for 1 minute or until sugar dissolves; stir constantly.
Remove from heat.
Cool completely.
Pour into a 13 x 9-inch baking dish.
Cover; freeze at least 8 hours or until firm.
Remove dish from freezer, and scrape the entire mixture with a fork until fluffy.
Store the remaining granita in an airtight container.
Cover and freeze up to 1 month.