why is brian not able to hit a fish with his arrow

In Hatchet, 13-year-old Brian Robeson is stranded in the Great North Woods after a plane crash and must struggle to survive while he awaits rescue. He learns by trial and error how to hunt, fish, gather edible vegetation, and keep himself warm and dry.
Brian first attempts to fish using a sharpened stick as a spear, stabbing at the fish through the water. The fish can sense the disturbance in the water, however, and dart away before he can catch any. Brian decides to use a bow and arrow instead, and after crafting these tools, he tries again to catch the fish, but somehow, despite his best efforts, his aim is never quite right.
Frustrated and angry, Brian almost gives up, before suddenly realizing that he has only been looking at the surface of the water when taking aim. He remembers that water refracts light—that is, it bends light waves, distorting the images of things under water. When he takes aim with the tip of his arrow under the water's surface, he can account for the refraction, and see what his arrow is actually aiming at. This method works well, and Brian is able to catch several fish.