Duunnn dunnn … duuuunnnn duun … duuunnnnnnnn dun dun dun dun dun dun dun dun: This is presumably the tune that plays in every swimmer’s mind when they wade into the open ocean. But it may just be the right light display, rather than the right musical intonation, that could keep that threat in the shadows.
While John Williams’ score helped strike fear into the hearts of moviegoers, in reality, the average person isn’t likely to be the victim of a shark attack. According to the Florida Museum of Natural History, only 69 shark bites, classified as unprovoked bites, were recorded worldwide in 2023 — which out of a global population of 8.2 billion people, is pretty good odds unless you are interrupting dinner.
The odds are substantially worse for surfers, though, because sharks often mistake them for certain types of prey, such as seals. This is because sharks, especially great whites, place a high reliance on their eyes to locate prey. Though they are colorblind and have poor visual acuity, great whites compensate with a knack for detecting silhouettes, which could lead to the jaw-dropping mistake of thinking a human-laden surfboard is a tasty meal.
Courtesy of iStock.com/Bullet_Chained.
Well, it turns out, that’s exactly what mosquitoes count on.
To curb this less-than-toothsome behavior, researchers at Macquarie University decided to test a counterillumination strategy at South Africa’s shark-infested Mossel Bay, using different configurations of LED lights on the underside of decoys to break up its silhouette. These 1.2-m-long foam decoys were made to look like seals and were tugged on a 20-m line behind a boat. The control decoys were regularly attacked by the great whites.
Their first test, which consisted of covering the whole of the decoy’s underside in bright lights, was found to work very well in deterring sharks. This was deemed impractical, however, because the lights were not energy efficient, too expensive, and thus impractical for regular use on a surfboard. Surfers are supposed to catch the wave, not transmit it, after all. Other types of light designs and patterns, such as strobes, were also tested but with less success.
Eventually, the researchers were able to find a winning formula to get the sharks to stop attacking the decoys: simply placing the lights in strips horizontally while the decoy was in motion. This is similar to how some animals take advantage of striped patterns in nature, as they can act as a type of disruptive camouflage that makes it harder for predators to see the outlines of potential prey.
This is good news for technologically capable seals. But the researchers were unable to test such strips on surfboards during the experiment, due to South African regulations. Nevertheless, they posit that the technique will transfer into safer wave riding. Part of the researchers’ plans for further study include trying out surfboards with embedded LEDs, as well as testing the technique’s effects amid other sharks, such as tiger sharks and bull sharks.
Generally, surfers need not wait for a commercial version of this shark deterrent to feel safe while taking a dip at a favorite beach. Unless, of course, they decide to surf in chummed waters. Then, it might be time to turn on the lights.