Plane mirror

As light incident is normal to the water surface and hence it will pass undeviated using geometry, angle of incidence of light on surface 1 is 45° and hence angle of reflection will be 45°, so light will move horizontally. Now, angle of incidence to 2 surface is 45° and hence angle of reflection will be 45° again. Normal incident light as wider surface will go without deviation. ∴ Total deviation=180°(direction just opposite).