In a small saucepan, add blueberries, sugar, lemon juice and 3 tablespoons of water, stir.
Heat over low/medium heat, stirring occasionally and bring to a boil. Let boil for about 4-5 minutes.
In a small bowl, mix remaining water and corn starch together.
Add corn starch mixture to blueberry mixture, stir until thickened then remove from heat and let cool.