These LED Lights Could Make Humans ‘Invisible’ To Sharks

SYDNEY — The silhouette of a surfer paddling on their board looks remarkably like a seal from below, at least to a hungry Great White shark. But what if we could make that silhouette disappear? In a new international study, marine biologists have found that underwater LED lighting can effectively make humans “invisible” to sharks, offering a potential for preventing attacks while preserving these critical ocean predators.

Published in Current Biology, the research reveals that Great White sharks are significantly less likely to attack seal-shaped decoys equipped with LED lights on their undersides. This lighting technique, known as counterillumination, mimics a natural camouflage strategy used by many marine animals to hide their silhouettes from predators lurking below.

The researchers explain that sharks primarily identify potential prey by spotting dark shapes against the bright background of the sky when looking up from below. The research team discovered that disrupting this visual pattern through strategic lighting dramatically reduced shark attacks on the decoys.

“It’s sort of like an invisibility cloak but with the exception that we are splitting the object, the visual silhouette, into smaller bits,” says study author Nathan Hart from Macquarie University, in a statement. “It’s a complex interaction with the shark’s behavior. The lights have to be a certain pattern, a certain brightness.”

Shark Responses to Light

The team conducted experiments off the coast of South Africa, an area known for its Great White shark population. They towed seal-shaped decoys behind boats and systematically tested how sharks responded to different lighting configurations. They found that sharks consistently avoided attacking decoys with LED lights on their undersides, while frequently attacking identical unlit decoys.

The lights didn’t need to cover the entire underside of the decoy to be effective. Horizontal stripes of light were particularly effective at deterring sharks, suggesting the pattern disrupts the shark’s ability to recognize the shape as potential prey.

Lighting that exceeded the brightness of the surrounding environment effectively deterred sharks. Counterillumination works by creating visual disruption rather than by perfectly blending with background light levels.

For surfers, swimmers, and other ocean enthusiasts, this discovery presents a glimmer of hope. Current shark deterrent technologies have shown mixed results or rely on methods that can harm sharks, a species already facing significant conservation challenges.

Shark Vision and Hunting Behavior

When researchers arranged lights in horizontal stripes across the decoys, sharks still avoided them. However, when the same amount of lighting was arranged in vertical stripes, some sharks did attack—suggesting that a long, narrow silhouette more closely resembles their typical prey.

Scientists used sophisticated motion detection models to analyze how sharks might perceive these different lighting patterns. They discovered that horizontally striped lighting creates confusing motion cues that may make it difficult for sharks to track the object accurately.

The concept draws inspiration from nature. Many marine animals, from squid to some species of fish, use bioluminescent organs on their undersides to match the brightness of downwelling light, effectively erasing their silhouettes from predators below. This is the first study to demonstrate the effectiveness of this strategy as an anti-predation mechanism against Great White sharks.

Modifying silhouettes could form the basis for new shark deterrent technologies that help protect human lives. This non-invasive shark bite prevention technology that could be integrated into surfboards, wetsuits, or other water equipment.

While these findings show promise, the research team cautions that more testing is needed before commercial applications can be developed. Different shark species hunt using different strategies, and testing would need to be expanded to species like bull sharks and tiger sharks that are also responsible for attacks on humans.

The effectiveness of counterillumination also might vary depending on water clarity, time of day, and other environmental conditions. The research team noted that their dim lighting configuration was sometimes attacked during late morning hours when contrast between the lights and background was lowest.

However, this solution doesn’t harm sharks or rely on repellents that might damage marine ecosystems. Instead, it simply takes advantage of the visual cues sharks use when hunting, making humans less likely to be mistaken for prey.

Many shark attacks on humans result from “mistaken identity“—sharks confusing humans, particularly surfers, with their natural prey like seals. By disrupting the visual silhouette that triggers predatory behavior, counterillumination technology could reduce these tragic interactions without harming shark populations.

Interactions between people and sharks will inevitably increase. Rather than turning to harmful shark culls or dangerous deterrents, using light to disrupt hunting cues might be the simple solution that allows humans and sharks to peacefully coexist in our shared ocean home.