A 15 foot GW is still considered a juvinile... meaning he/she is not completely schooled in what's food and what isn't. They learn the same way we do... through experience. It sucks whenever you hear about a surfer or diver attacked, but I can't find it in my heart to feel sorry for them. They know the risks of being that far off shore in known shark inhabitated waters. If they don't know the risks they are ignorant and get what they ask for. Although GWs are classified as 'loner sharks' they are known to hunt in groups. They will travel along learned food routes together... a small pack of sharks can hunt seals more succesfully. A few sharks will 'line up' along the reef to prevent the seals return to shore. Then one by one they will move in to take advantage of any mistakes the seals might make. They are very calculated in their methods. The reason you hear about surfers being hit by sharks is because they surf in the same waves that seals swim... not smart. If you see a beach loaded with seals don't go in the water. I can guarantee you that there are at least 5 GWs swimming in the deep waiting for something to enter the water. From underneath, a surfer will resemble a seal resting on the surface... sharks don't have clear vision like you would expect. Being the unlucky victim of mistaken identity blows, but sharks have to eat too.