A recent cluster of four shark incidents along the New South Wales coast highlights how current environmental conditions are driving sharks closer to shore and increasing the likelihood of human interactions.

All four incidents occurred within a few hundred kilometres of each other, at a time when the region has been heavily affected by intense summer rainfall. Floodwaters have pushed large amounts of fish, nutrients and debris out of rivers and into estuaries and near-coastal waters. These conditions create ideal feeding opportunities for sharks close to popular swimming and surfing areas.

At the same time,  high offshore sea surface temperatures are being recorded off Sydney and further north, reaching almost 27 degrees. These warm offshore waters are relatively poor in nutrients and support fewer fish. In contrast, inshore coastal waters are currently almost seven degrees cooler and far richer in marine life.

This temperature and nutrient difference effectively concentrates prey closer to the coast. Sharks follow the food. When rivers are flowing and coastal waters are murky and productive, sharks are more likely to be present near beaches and headlands.

The situation is further compounded by peak summer holiday season, with large numbers of people in the water every day. The combination of environmental drivers and increased ocean use has resulted in a higher-than-normal risk period for shark incidents.

While the overall likelihood of a shark encounter remains low, simple precautions can greatly reduce the risk:

• Do not swim or surf at closed beaches or where warnings are in place
• Avoid headlands, river mouths and areas near estuaries
• Stay out of murky or discoloured water, especially after heavy rainfall
• Avoid swimming at dawn, dusk or at night when sharks are more active

Understanding the current conditions helps people make safer choices and puts the number of incidents into perspective.

Beachgoers are encouraged to follow local council and Surf Life Saving advice, check shark alerts, and always swim at patrolled beaches.

"The risk of shark bite is difficult to predict and a range of factors can contribute to trends in shark sightings and shark bites. We’ve recently done a review on the factors influencing the number of shark bites and found 40 factors suggested to affect shark risk. Human population growth, habitat modification and destruction, declining water quality, climate change and anomalous weather patterns, and changes to the distribution and abundance of sharks and their prey are all often proposed to explain the recent increases in shark bites. However, the infrequent occurrence of such events reduces our ability to determine which of these factors explain the increase in shark bites the most. It is likely to be due to a combination of these factors (rather than just one). Our review tried to identify scientific studies quantitatively testing the effects of some of these factors and there was a lack of consensus among studies on the effects of these factors.

Globally and in Australia, the number of shark bites has increased over the past four decades. However, shark bites are decreasing in some regions and remain stable in others, reflecting the high variability of the risk of being bitten by a shark.

The recent cluster of shark bites in the Sydney region is unusual, but similar clusters have previously occurred in Australia (e.g. Margaret River WA, Far North NSW, Cid Harbour Qld, West Coast of SA) and overseas (e.g. Egypt, Reunion Island, New Caledonia). The reason for these clusters of bites is unknown but is probably related to environmental (or other) conditions increasing the likelihood of humans and sharks being nearby each other. In the case of the recent events in Sydney, the warmer summer water temperature and recent high precipitation likely increased shark activity and probability of people encountering bull sharks.

If journalists want more specific details about the history of shark bites for the Sydney region, they should go to the Australian Shark Incident Database: https://taronga.org.au/conservation-and-science/australian-shark-incident-database

Shark-bite mitigation effort has increased exponentially over the last decade and the NSW state government has substantially invested in traditional and novel methods to reduce the risk of shark bites, with NSW DPIRD having developed and implemented a world-leading shark management program."

“Summer is a time when both people and sharks are more active in the water - warmer temperatures, moving marine life, and higher numbers of people using the water increase the chance of overlap.

“There are steps people can take to reduce risk such as avoiding swimming at dawn and dusk or after recent rain events – conditions that are both conducive to more shark activity – as well as swimming between the flags and following the advice of state governments and their SharkSmart programs.

“You can’t reduce your chance of a shark encounter completely to zero. These are shared environments and sharks play an important role in marine ecosystems. We need to be careful to use evidence-based approaches to balance that with keeping people safe.”

“Three main factors would increase the likelihood of human-shark encounters in the current context off the Australian east coast:

• Storm/heavy rain conditions - stormwater runoff from heavy rain brings nutrients (from sewage and agricultural waste waters) into estuaries and coastal waters, which attracts baitfish, and thus larger predators.
• Murky waters - bull sharks are not only a unique species that can live in marine, estuarine (brackish), and freshwater environments, but also are opportunistic predators that thrive in brackish water. They are naturally attracted to these areas to feed.
• Extended species range and summer season - increasing water temperatures due to climate change are causing many fish species, including sharks, to spend more time in higher latitudes (farther south for bull sharks) and, in some cases, to stay longer rather than migrating to warmer waters for winter. Recent research by Lubitz et al. (2025) indicates a 0.67°C rise of sea surface temperatures in coastal waters off Sydney, with sharks increasing their residency time by roughly 15 days over the past 15 years (1~ additional day per year). In other words, this research found that bull sharks off the eastern coast of Australia were spending more time on their summering grounds (shallow, inshore, estuarine areas).

The extended window of time in which bull sharks and humans are in the same place, due to the factors above, needs to be accounted for when we make decisions whether to enter the water in given areas.”

"Shark encounters are an unavoidable possibility of using oceans for leisure and recreation. Community debates continue over the value of shark nets and barriers, with increasing opposition to their use, as they offer little protection to people and lead to the deaths of many marine animals. Shark bite mitigation measures, such as drones, tagging programs, and increased public education about when not to swim and surf, will offer more protection while also protecting the lives of sharks.

My research shows that the growth in popularity of drone footage of shark encounters with people has led to increased awareness of the presence of sharks, as well as some shark behaviours. This has led to further understanding of the conditions that accompany an increased shark presence, such as storm runoff, fish and bait balls, and whale deaths. Swimmers and surfers often refer to this footage, and use it as evidence of what they already know – that they share the water with sharks."

"There are some things folks can do to minimise the risk of shark bites.  Keep in mind that being bitten is very rare indeed, so we are tinkering at the edges of probability.

First, avoid swimming on your own - this is a general rule for safe swimming, but it equally applies to sharks. If someone gets bitten, you need to seek help as fast as possible.

Second, avoid swimming at dawn and dusk - this tends to be a time when sharks are more active.

Third, don't swim after heavy rainfall, especially in and around estuaries. Sharks, especially bulls, are drawn to freshwater flushes to feed on fish and dead animals as they drift down from rivers. Analysis of bull shark catches close to shore always shows an effect of rainfall.

Fourth, don't swim in murky water (also associated with high rainfall). Sharks' vision for finding prey will be impeded, and they will be attracted to disturbances in the water. They are more likely to accidentally bite a person, thinking it is prey (sharks do not eat people).

Given the incredible rainfall we have had of late, the risk of encountering sharks is high. Stay out of the water till it clears."

"First and foremost, any injury in the ocean is confronting, and it is important to approach this conversation with care and respect for those affected by these very serious shark-human interactions. It is also important to frame these as shark-human interactions rather than deliberate attacks. Sharks do not target people.

From my work in shark physiology and how environmental stressors shape their energy budgets, movement, and performance, we know sharks move through coastal environments in response to food, temperature, and changing ocean conditions. Occasionally, those pathways overlap with where people swim, surf, and fish.

Right now, along the NSW coast, we have seen a combination of very warm water, active weather systems, and recent heavy rainfall. Storms and river outflows create flood plumes that carry nutrients and fish into coastal waters, which can attract prey species and, in turn, predators like sharks. Coastal species, like bull sharks and some whaler sharks are particularly known to move toward these plumes because they are following food and favourable conditions, not people.

Bull sharks are also one of the few species of sharks and rays that can tolerate brackish and even freshwater for extended periods, which means they are especially comfortable moving in and out of river mouths and turbid coastal waters after heavy rain.

We also have more people in the water than ever before, which naturally increases the chance of encounters. The key message is being shark smart... understanding environmental cues (i.e., avoiding turbid waters after storms), following local advice and beach closures, and recognising that we are sharing a dynamic, changing ocean. Sharks are a sign of a functioning ocean, not a broken one."

"The spate of shark bites in NSW over the past day is very unfortunate. Whenever there is a shark bite, it deeply impacts not only the individual and their loved ones but the wider community. It is important that this is front and centre when discussing shark bites, especially the politics of mitigation.

Importantly, from a fear of shark/shark perception perspective, it is important to understand the context. We do know that weather events such as storms can impact the visibility of the water, which can mean sharks misidentify people as prey (e.g. seals or turtles). Sensationalisation of events like this can lead to exaggerated/ongoing fear of sharks, which can impact people’s relationship to the ocean broadly, and also lead to support of ineffective mitigation strategies like nets. Instead, we need to focus on other types of mitigation, such as educating the public, surveillance, and other innovative approaches."

"Children and adults may be rightly fearful of now swimming at these much-loved beaches. It is important to have honest conversations with children about their fears and to ensure that they are given accurate information.

Some children might need to be re-introduced to the water with a trusted adult when there has been clearance to swim. Staying in visible water has also been recommended."