Sharks don't fear you, they just ignore you

Many studied shark species, including large predators, appear to be colorblind. They live in a perpetually grayscale world, one where the subtle color differences that help many predators identify prey are completely lost. This means a vibrant coral reef looks like a monochrome photograph to a shark. This limited visual spectrum is a key factor in why sharks rarely seek out humans.

Sharks have rod-dominated retinas, meaning their eyes are optimized for detecting motion and contrast in low light conditions, common in deeper waters or during dawn and dusk hunts. While this gives them incredible night vision, it comes at the cost of color perception. To a shark, a swimmer or surfer on the surface likely appears as a dark, indistinct blob against the brighter sky, making it difficult to properly identify. This visual ambiguity reduces the chances of a deliberate predatory attack.

When bites on humans do occur, they are often described as 'investigatory.' A shark might be trying to determine what a novel object is using its mouth, which is packed with sensory cells. This isn't a malicious attack; it's more like a curious dog sniffing something new, but with potentially devastating consequences given a shark's anatomy. Because sharks rely on contrast and silhouette to identify prey from below, the shape of a surfboard can closely mimic that of a seal. This can lead to a 'taste test' out of pure curiosity.

Many shark species are designed to hunt specific prey that are abundant in their environment. Humans are not a natural part of their diet, nor do we typically exhibit the movements of their usual quarry. The energy expenditure of chasing and subduing an unfamiliar, oddly shaped creature like a human often outweighs any potential caloric reward. So, while a shark might not "fear" us, they also generally don't see us as food, preferring to stick to what they know.