Wearing stripes might help, and the reason you’re safer inbetween the flags isn’t necessarily because of the crowds.
We asked marine ecologist and senior lecturer at Southern Cross University, Dr Daniel Bucher how best to minimise your chances of having an encounter with one.
Should you wear stripes?
Surfers and divers have long been warned to swap bright-coloured swimsuits for dull ones, and avoid wearing jewellery or anything shimmery in the water, but there's also the idea of designing your attire with shark repelling in mind.
“They now believe that most sharks - if not all - are colour blind,” says Dr Bucher, “So it’s not so much the actual colour but the contrast in colour that might be important. That’s why there’s been work on developing contrasting stripes for the bottom of surfboards or wetsuits.”
There are two separate theories as to why this contrasting pattern may work. One idea is that black and white (or black and yellow) stripes break up your outline so you look less like a meal.
Bucher counters this point however, saying “most shark attacks would be on surfers from below where they’re silhouetted against the light; the board’s going to be in shadow anyway regardless of the colour”.
Another theory is that highly contrasting colours and patterns in nature often signal something poisonous or dangerous, so it could deter sharks for that reason.
Whether stripes have a significant impact on lessening attacks is yet to be determined, according to Bucher.
But simply attaching a sticker with contrasting stripes to the bottom of your surfboard is a low cost, low technology solution that may be worth trying regardless.
The less you act like a flailing fish the better
Sharks hunt by sensing the electromagnetic field around objects in the water, so each splash or kick sends out a wave that the sharks can pick up thanks to a jelly-like substance in their heads. It allows them to have an idea of how large and how active an object is without even needing to see it.
They are particularly attracted to indications of an injured fish or mammal - easy prey - so it’s best to avoid movements that indicate you’re struggling on the surface of the water.
Ideally, “you want to be moving smoothly and as efficiently as possible to try and look like you’re not injured,” Bucher says.
Consider a shark shielding device
There are now a range of shark repellent devices on the market “that generate a strong electromagnetic field that basically overstimulates the shark’s senses,” Bucher explains.
“The theory is that it gives it an unpleasant sensation rather like yelling in someone’s ears or shining a bright light in someone’s eyes. If it’s a shark that’s approaching cautiously, like most of them do when approaching a human (as we’re quite a big animal that might potentially be dangerous to the shark) and they get that unpleasant sensation, that can often be enough to put them off.”
Research has found that the devices do have an effect on a shark’s behaviour in a way that may reduce the chance of an attack (however, the studies didn't involve humans, and instead used an attractive tuna burley lure).
The downside is that ocean swimmers can find these devices cumbersome as they create drag when attached to their ankles. They also cannot be used in areas around threatened grey nurse sharks.
Spear fishing attracts sharks
Spear hunting is particularly dangerous due to the “vibrations caused when the gun goes off, and the vibrations caused by the dead or dying fish.”
It is actually these vibrations, rather than any blood in the water, that attracts sharks most strongly. As Dr Bucher explains, “sharks have a very good long distance sense of vibrations in the water, particularly vibrations that indicate an injured animal.
“Blood has to actually be transferred to them and yes, they can sense blood in the water at very low concentrations, but it still has to get to them. So it’s probably not the thing that would attract them from a great distance.”
Bucher says these vibrations are such strong indicators that he’s heard of places along the Great Barrier Reef where simply firing a spear gun in the water three times will beckon the predators who are so used to associating that sensation with food.
Another reason to swim between the flags
You are very unlikely to succumb to a fatal shark attack when swimming between the flags. “The safest place to be is where there’s a lot of eyes watching,” says Bucher and jokes, “The surf lifesaving people love to cite that their record of preventing shark attacks!”
What lowers your chances of being approached by a shark isn’t necessarily the number of people around but rather the conscious efforts taken to minimise the risk for your benefit.
What you may not know about dawn and dusk
It’s widely known that you’re more likely to see sharks when the sun is rising and setting.
“Overall you generally do find more shark activity at dawn and dusk, which is particularly true for reef sharks,” says Bucher.
Dawn and dusk is when local fish populations change over, as those that are active during the day head off to seek shelter, while nocturnal fish come out to forage. For sharks that makes for ideal hunting time, increasing the kinds of fish they can prey on. But it's not true for all sharks.
“Great Whites tend to attack at any time of the day,” Bucher explains, “It’s much easier to eat seals during daylight. When we talk about sharks, we talk about a range of species within different habitats and with different habits, so some of their behavioural rules don’t hold true for all sharks.”
Avoid seals and feeding birds
Wherever there is food, there will be predators - so when you see animal activity in the water, it’s probably best you keep your distance.
As Dr Bucher says, “if you’re at the beach, certainly bait fish, birds feeding and dolphins feeding are often a sign that sharks are also feeding.”
Steer clear of dirty water and watch out around underwater trenches
Murky waters like those stirred up by heavy rainfall are always best to avoid. Sharks don’t need great visibility to hunt and “being scavengers, they’ll be hanging around river mouths and dirty water on beaches looking for easy food,” says Bucher.
Meanwhile, places where there are natural changes of depth on the sea floor can be attractive spots for sharks. “In very general terms, where you get rapid changes in depth is often a place where sharks will patrol up and down on the edge of the deep water so trenches and channels and so on can be a place where you have a higher likelihood of encountering a shark,” Bucher says.
What to do if you come face to face
If you see a shark and are able to get out of the water, you should do so. Bucher offers another suggestion if that isn’t the case, saying “the last option is actually to take the offensive and swim at it."
The idea is that by turning to approach a shark, you're acting differently to the way escaping prey normally would, and may make the animal re-evaluate the danger in approaching you. "It might give you that little moment that you can then get out of the water, it could just increase that space between you," he says.
Dr Bucher bases his theory on a test he conducted at Sea World in which a two metre shark was stalking a mini submarine device about the size of a football. Every time they turned the device around and had it swim directly at the shark, the animal’s response was to swim away.
That said, Dr Bucher believes “it might only work on a cautious animal” and very likely not for a five metre shark.