A shark lunged at Alex while his back was turned. The ‘helmet’ on his ankle may have saved him

The early morning sun had just risen over Dee Why when a suspected bull shark lunged for Alex Preston’s legs.

He had already surfed a handful of waves at his local break when stunning beach camera footage captured the shark lunge and splash at Preston as he curls onto a wave, riding away from danger as a dorsal fin breaks the surface.

It was the last wave Preston caught that morning. Only when he returned home did he realise just how close the shark came after his wife pointed out the near miss when they reviewed the footage.

The encounter occurred weeks after an 11-year-old was knocked into the water by a shark on the same break, and across the headland from where Mercury Psillakis, Preston’s “wonderful friend”, was fatally mauled at Long Reef in September.

He credits some good fortune for the near miss in mid-February. However, he was also grateful for the shark deterrence safety band he was wearing, which he likened to a “bike helmet” strapped to his ankle.

“It had a crack at my legs … it was quite a banal interaction until I saw the video and got the full picture of it,” Preston said.

“I had my shark band on my foot, and I assume it must have kept the shark at bay.”

Preston is among a growing number of Sydney surfers wearing deterrence bands following a horror run of shark attacks across the NSW coastline in the past six months.

The bands, worn on the wrists and ankles, create an electromagnetic field that irritates the electro-receptors sharks use to navigate the oceans and stalk prey. The effect on the shark has been compared to shining a bright light on a person in a dark room.

Sharks can resist the unpleasant sensation, and the device’s effectiveness depends on several environmental and situational factors. This includes the number of sharks in the water near the person and how quickly the device is moving.

Testing shows sharks display avoidance behaviour at a range of 0.5 metres to 2 metres. Results from Western Australia’s Department of Primary Industries and Regional Development in 2021 showed sharks “abruptly” changing course when near the device.

The bands are among several shark deterrents on the market, which also include camouflaging wetsuits and surfboards designed to disguise surfers in the water column.

They are essential for Nick Rendall, a diver who runs an underwater boat cleaning and maintenance business on Sydney Harbour. He and his employees wear the bands “religiously” as they often dive in murky and brackish water with limited visibility – conditions known to attract sharks.

“I think if you combine something like a shark band with a bit more knowledge of shark behaviour, you can really make sure all these shark attacks that have happened don’t happen,” Rendall said.

“The science behind it makes sense, and then also knowing is like, well, I’ve got protection. It definitely provides a nice peace of mind.”

Holly Cummins wears two of the bands in the surf since she was almost attacked by a two-metre bull shark in the waters off Killalea Regional Park on the South Coast last month.

“I didn’t see it coming – a surf mate witnessed it from behind me, he said it came up behind my board, exploded then thrashed around a few times before disappearing,” Cummins said.

“It would have been a very different outcome had I not been wearing the band.”

Nathan Garrison, co-founder of Sharkbanz deterrent bands, reported a 30 per cent rise in sales from Australia in January, a month in which 12-year-old Nico Antic was killed by a shark in Sydney Harbour and South Coast musician Andre de Ruyter required a leg amputation after he was mauled at Manly.

Garrison acknowledged it was difficult to know how much the uptick was due to the attacks but said demand was definitely higher as ocean users looked to protect themselves.

“Deterrents can be part of that [response], but understanding what’s driving the additional shark activity and how to avoid high-risk areas is super-important too,” he said. “These are safety devices, and they can’t eliminate risk altogether.”

University of NSW Professor Dewei Chu said the devices were a good idea, as they “disturb the navigation of the shark, to make it get lost”.

Garrison said surf lifesaving and boardrider clubs were among organisations showing new interest in the deterrence bands.

Results indicate the bands are most effective against bull sharks, the species suspected to be behind four attacks within 48 hours on NSW beaches in January, including those on Antic and de Ruyter.

Chu preferred the bands to shark nets – responsible for the deaths of more than 200 sea creatures in the 2024-25 summer – and advised they be combined with other safety strategies in the water.

“In that case we can have very good protection for people who are swimming or diving … I think this is the future.”

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