Combine rhubarb, sugar and water in a 1 quart saucepan.
Cook over low heat, stirring frequently, for 15 - 20 minutes until the rhubarb is soft.
Puree in a blender and refrigerate until completely cool.
Combine cooled rhubarb mixture, cold cream, vodka, if you are using it, and sea salt.
Pour into an ice cream maker, and churn according to manufacturer's instructions for 20 - 25 minutes.