Caramel Sorbet

In a dry heavy saucepan cook sugar, undisturbed, over moderate heat until it begins to melt and continue to cook, stirring with a fork, until it is melted completely and a deep caramel. Remove pan from heat and carefully add water down side of pan. Return pan to heat and cook caramel, stirring, until it is dissolved completely. Stir in salt and vanilla and chill until cold. Freeze sorbet i