Preheat an oven to 350 degrees F (175 degrees C). Grease 18 muffin cups, or line with paper muffin liners.
Mix together mashed bananas, egg, water, and oil in a large bowl. Mix in flour, baking soda, and baking powder until mostly smooth (you will still see lumps from the banana, but that's okay!). Gently fold the blueberries into the batter.
Bake in the preheated oven until golden and the tops spring back when lightly pressed, about 15 minutes. Remove muffins from tins, and cool on a wire rack.
Frost is a common problem with wild blueberries and is the primary cause of a poor harvest. Not all blueberry farms have the same climate. The fields in Quebec and Maine blossom before the fields on Prince Edward Island and are therefore more susceptible to frost. The later blossoming of Island berries usually occurs after the last frost of the spring.