Great whites and other sharks hunt from below, relying on the contrast of their prey backlit by the light above. There are many similarities between a seal and surfer from this angle are significant, especially to a shark.
Like many sharks that bite people, the animals view their surroundings in fewer “frames” per second compared with humans. Their color perception is also mostly limited to shades of blues and greens, and they cannot resolve shapes as accurately as we do.
The researchers also point out that sharks have an acute sense of smell and an ability to detect vibrations through the water, which may explain why shark attacks remain extremely uncommon despite the visual similarities between humans and their preferred prey.