In a large bowl combine the flour, coconut, sugar, baking powder and salt. Add the eggs and ricotta then stir until not-quite mixed with some floury patches remaining. Sprinkle the frozen blueberries with some extra flour and stir to coat. Add the flour-coated berries to the batter and stir in very gently until just mixed. Set aside for 15 minutes.
Meanwhile heat a 2 inch depth of vegetable oil in a large saucepan to 365 F (185 C).
Using two oiled spoons, drop rounded tablespoons of batter into the oil. Fry until golden brown then flip and fry until the other side is golden brown (about 4 mins). Remove the doughnuts to a paper towel-lined plate to drain.
Place the powdered sugar in a small bowl, pour in water 1 tsp at a time, stirring between additions until you have a pourable glaze. Dip the warm doughnuts into the glaze, turning to coat. Transfer to a piece of parchment paper and sprinkle with desiccated coconut then leave to set.