Boil water & sugar together for 5 minutes. Cool. Stir in juice and peel. Pour into shallow bowl and put in freezer.
As it starts to freeze, keep stirring the outside crystals into the center and mix in peel. Do about every half hour. When real slushy, stop and freeze overnight.
To serve you must scrape very thin layers of the slush off the top. I use a big spoon with sharp edges moving it sideways.