In a large bowl, prepare the cake mix by mixing it with water, eggs and oil (follow the instruction on the box). Finely grate the orange peel (reserve a little bit of zest to garnish, if wanted). If wanted, you can toss 3/4 cup of blueberries in a little bit of flour and incorporate delicately to the dough with the zest.
Distribute the dough in 18 greased muffin tins. Distribute 1/2 cup of blueberries on each cupcake. Cook in the center of a preheated oven of 325 F for 22 minutes or until a toothpick inserted in the center comes out clean.
Meanwhile, press the orange to obtain 1/4 cup of juice. In a small saucepan, bring to boil the orange juice and remaining of blueberries. Reduce heat and let simmer 5 minutes (add sugar if wanted, but just a little bit). Let cool. Serve the cupcakes with the blueberry syrup and garnish with orange zest if wanted.