Temperatures are soaring and waters are warming, pushing more people into the water for longer and potentially moving sharks closer to shore.
After a woman was bitten on the leg by a shark while swimming in Elizabeth Bay in Sydney harbour on Monday, we asked experts whether shark bites are on the rise in Australia and what you can do to stay safe.
Here is everything you need to know.
How safe is it to swim in Sydney harbour?
Sydney harbour is home to a broad diversity of sharks and rays, “the vast majority of which are of no threat to people”, says Dr Vincent Raoult, a postdoctoral fellow at Macquarie University.
But white sharks, tiger sharks and bull sharks do swim in the harbour and are potentially dangerous.
Shark bites in Sydney harbour are rare. According to the Australian Shark Incident Database, there have been 36 shark bites in Sydney harbour since 1791. Excluding this week’s incident, the last was in 2009, according to the database compiled by Taronga Conservation Society Australia, Flinders University and the New South Wales Department of Primary Industries.
No shark-related deaths have occurred in Sydney harbour since 1963 but a man was killed by a great white shark at Little Bay beach in Sydney’s east in 2022.
Bull sharks tend to reside in Sydney harbour in summer before moving to the Brisbane River in winter, says Dr Chris Pepin-Neff, the author of Flaws: Shark Bites and Emotional Public Policymaking.
Warmer months from November to March are also when the vast majority of bites occur, Raoult says.
Australia averages 10 to 15 shark bites a year, 10% of which are fatal, Pepin-Neff says.
“Of all the harbours of the world, Sydney is probably one of the most used for actual swimming – people anchor their boats and swim,” Pepin-Neff says. “But Sydney harbour in the last 40 years has had very few shark bites.”
Raoult adds: “I think if you put it into perspective, the number of people that actually go in the water every day … it really shows that this is something that is not a common occurrence.”
How do I stay safe while swimming?
“The occasions where sharks have bitten people with the intention of actually eating are incredibly, incredibly rare,” Raoult says. “Humans are not really something that they like to eat. We are just not fatty enough.”
Exploratory bites are a common reason behind shark incidents, Raoult says. “Sharks are unsure of what a person is doing in the water. We are a foreign thing.
“Sometimes a shark may be curious … Most of their sensory capabilities are centred around their mouths and teeth, so they will do what is called an exploratory bite which, unfortunately if you are talking about a big predator like a bull shark, can be life-threatening for a person.”
Accidental bites also occur, especially when the shark encounters a person while feeding in a school of baitfish, Raoult says. He urges people to avoid swimming among the fish.
“Those usually mean sharks are around,” he says. “If they are in a feeding mode, and they suddenly run into [a person] that can have pretty bad consequences.”
Pepin-Neff says most shark bites happen between 12pm and 2pm “because that is when the most people are in the water”.
But bull sharks tend to spend most of the day “deeper down within the harbour”, Raoult says. When it is cooler, they come closer to the surface to feed – part of the reason experts warn people to avoid swimming around dawn and dusk.
“That is the period that overlaps with bull sharks out in the shallows looking for food,” he says. “That means they are more likely to interact with a person.”
It is safer to swim in Sydney harbour in winter, when bull sharks move to Brisbane River.
Being conscious of how far out we swim is also important. “The further out you are, the more dangerous things become,” Pepin-Neff says. “You are further into their territory” where water can be murky and it can be more difficult to see a shark approach.
Pepin-Neff recommends avoiding swimming in locations without enclosures and warns that shark nets can be unreliable.
And a final piece of advice: if you ever encounter a bull shark, “never swim away”.
“There is always this perception that you will see the animal before it wants to bite you, which I don’t think happens very often,” Raoult says.
“You always want to try to intimidate an apex predator,” Pepin-Neff says. “If a bull shark were near you and you were to swim away from it, it would come up and bite you.
“That tells it instinctively that this could be prey and I should follow it.
“But if you stay facing it, and potentially swim a little bit backwards or sideways, that is much safer, if the water is clear enough.”
Raoult adds: “Certainly remaining calm and slowly making your way out of the water is much better than panicking and trying to swim away.”
Are there more sharks around?
As climate change warms water, shark encounters with people are potentially becoming “a little bit more common”, Raoult says.
“The waters are warmer for longer, and so the amount of time that the shark spends in Sydney harbour and other areas around Sydney is increasing over time.”
In general, there are not more sharks, we are just seeing more of them, Raoult says.
“The keyword there is seeing.” Improved camera technology, including drones, means “we see sharks more often than we used to”.
“These sharks get really close to people very often. We just kind of never noticed them.”
Sydney harbour is cleaner and has more biodiversity than it did 20 years ago (after a change to the sewerage system and improved piping), making it a more dynamic ecosystem with “a lot more going on”, Pepin-Neff says.
There has also been a shift in ecosystem patterns as waters warmer. Fish behaviour changes, causing shark behaviour to change – including sharks getting closer to beachgoers, Pepin-Neff says.
On top of that, with warmer days, more people are driven to the water. “So you have got sharks that are closer to land, conditions that push more people into the water and a more dynamic ecosystem,” Pepin-Neff says.
“Those three things will necessarily increase the amount of times people and sharks interact, and leads to shark bites.
“It is really quite a diabolical combination.”
