Add berries and water to a blender and puree well. Pour the blueberry puree through a fine mesh sieve to remove most of the skin. (Some will still remain, if the skin doesn't bother you, omit this step)
Take 1/2 cup of the blueberry puree and add to a saucepan with 1/3 cup sugar. Whisk consistently until the sugar dissolves and is simmering. Remove from heat and let cool, then add to the rest of the puree.
Add a spoonful of blueberry mixture to the bottom of a large glass, then top with 1-2 scoops of vanilla ice cream. Add more blueberry mixture, then fill the rest of the way with club soda and stir.
Garnish with fresh mint and enjoy!