To make the syrup, add the blueberries, sugar, and water to a small saucepan. Cook on medium, stirring often to break up the blueberries. Cook just until it comes to a simmer and the sugar dissolves, about 3 minutes. Taste and add more sugar if you like a sweeter lemon-lime drink. Remove from the heat and strain out the blueberry solids.
To a small pitcher, add the coconut water, lemon juice, lime juice, and blueberry syrup. Stir well. Add ice to the pitcher. Pour an even amount of cold coconut water drink into 3 glasses. Garnish with lime slices and serve.