This no-bake pie shouldn't get watery; however, if the fresh blueberries that are added to the cooked berries are very wet, that may cause the pie to get watery. Baked blueberry pies sometimes are juicy or watery. It could be that the pie was underbaked; a baked blueberry pie needs ample time in the oven. Make sure you use enough thickener. Cooling the pie completely before slicing it helps too.