Sydney's sea now stays above 19°C (66°F) nine months a year. A century ago it was six.
In three lines
Right now
19°C is 66°F. Today's readings are at the beach. The 19°C line comes from monthly averages for the open sea offshore, so treat today's numbers as a guide.
The line
Two of the three sharks that matter stop at 19°C.
White, tiger and bull sharks cause almost every serious bite in Australia. Each dot below is one bite since 1900, placed at that month's sea temperature where it happened.
Below 19°C19°C or warmer
View as a table
Tagging agrees. Bull sharks fitted with acoustic tags leave Sydney once the water falls to about 19–20.5°C, and they have been leaving later each year as the sea warms (Lubitz et al., 2025).
The season
The warm season is getting longer. So is the bite season.
Seasons are southern hemisphere: summer is December to February, autumn March to May. The grid shows how often each month's sea temperature averaged 19°C (66°F) or more, by decade, at the beach you pick; months run July to June so summer sits in the middle. Below it: in which season bull shark bites happened, then and now.
The warm water has moved south. Bull shark bites are following, slowly.
Four eras side by side, oldest on the left. Each column shows where most bites happened on the Queensland and NSW coast (the middle 80%) and how far south the sea stayed at 19°C or more for at least half the year. Pick an era to see its bites on the coast.
Where most bites happened, one column per eraCenter of the zoneWhere the sea is 19°C or more half the year
Bull shark bites by decade. They have been here before, and they are climbing again.
Coastal watersEstuary, harbor or river
Bull shark bites have moved out of estuaries, harbors and rivers into coastal waters.
Share of all bull shark bites in Australia that happened in coastal waters rather than in an estuary, harbor, river or lake, by era.
View as a table
Coastal watersHarbor, river, lake or estuary
The bigger picture
The ocean is one connected system. Every change ripples through it.
The 19°C line moving off Sydney is one local sign of a global change. The ocean soaks up most of the heat trapped by greenhouse gases and much of the carbon dioxide, and the seas around Australia, especially the Tasman Sea, are warming faster than most. Warmer, more acidic water changes where plankton, fish, turtles and whales live, and the sharks that eat them follow.
The warm current+350 kmThe East Australian Current now reaches about 350 km further south than 60 years ago, and the sea off eastern Tasmania is warming up to four times faster than the global average (Ridgway 2007, via Redmap). It drove the record 2015–16 Tasman Sea heatwave, 251 days long; climate change made a heatwave that long at least 330 times more likely (Oliver et al. 2017).
Australia's seas+1.08°Csince 1900. The Tasman Sea, off Sydney and Eden, is warming at twice the global rate as the East Australian Current pushes further south (CSIRO and Bureau of Meteorology, 2024).
Where the heat goes90%+of the extra heat trapped by greenhouse gases ends up in the ocean. 2025 set a new record for ocean heat, the ninth year running (Eos, 2026).
Marine heatwaves+54%more heatwave days a year worldwide in 1987–2016 than in 1925–1954; heatwaves also became 34% more frequent and 17% longer (Oliver et al. 2018).
Ocean chemistry~30%more acidic than before the industrial age (pH about 8.2 down to 8.1), because the ocean absorbs about a quarter of the carbon dioxide we emit (European Environment Agency).
Marine life on the move+72 kma decade: how fast ocean species are shifting toward the poles on average, about 12 times faster than species on land, from 1,735 recorded changes worldwide (Poloczanska et al. 2013).
In short: a change in one part of the ocean moves the whole food web. Warmer water reaching further south and staying longer means prey, predators and people now share more of the coast for more of the year.
Not just Australia
Other oceans show the same pattern, measured in different ways.
If warming is moving sharks here, it should be happening elsewhere too. It is. These studies used tags, satellite tracking and fish surveys, not bite records, so they are independent evidence.
Every shift points away from the warm tropics. Teal arrows are worldwide, in both hemispheres; dotted means a projection. A simplified diagram, not to scale.
+400 km
Tiger sharks reach further north for every 1°C of extra warmth, about 14 days earlier. Nine years of satellite tracking, 40 years of tags. StrongHammerschlag et al. 2022
+500 km
Young white sharks on the US Pacific coast pushed north into Monterey Bay in the 2014–16 heatwave. 22 million tag readings. StrongTanaka et al. 2021
+1,000 km
Whale sharks' core habitat is projected to shift more than 1,000 km by 2100, about 12 km a year, in both hemispheres. From satellite tracking and climate models. ProjectionWomersley et al. 2024
+72 km
a decade: how fast ocean species are moving toward the poles on average, worldwide, from 1,735 recorded changes. About 12 times faster than on land. StrongPoloczanska et al. 2013
Southern hemisphere: outside Australia, few long-term shark records exist yet, which is part of why Australia's own data matters. Australia's shift is covered in the sections above.
Beyond range: what else is changing elsewhere
Tiger shark US Atlantic
Arriving earlier
14 days
Usual
+1°C
In years when the sea was 1°C warmer than usual, tiger sharks reached the US northeast about two weeks earlier, and travelled further north. Strong
Young bull sharks in Mobile Bay rose fivefold from 2003 to 2020 as it warmed; Texas bays up to eightfold over 40 years. In North Carolina, 53 were reported in 2011–16 against 6 in the eight years before, as a new nursery opened. Links, not proof of cause. Strong
Off California, the band of water just right for young white sharks, warm enough but not too warm, has been shrinking since 1982. In the 2014–16 heatwave they were pushed about 500 km north. Strong
Whale sharks are projected to lose more than half their core habitat in some countries' waters by 2100 under high emissions, as their range shifts more than 1,000 km. Projection
Days 1–3Four bites, January 2026Sydney Harbour, Manly, Dee Why, Port Macquarie.
72 hoursHarbors and riversOfficial advice: wait 72 hours.
About 4 daysFemales followTracked females shift upstream.
TrackingBitesSafety advice
After heavy rain
The fastest-changing risk: days, not decades.
1 to 4 daysBull shark Sydney Harbour
Ten years of tracking 177 bull sharks and fish together found heavy rain moved all of them: males upstream within about a day, females within about four, and sharks spreading along the coast after big rain. StrongNiella et al. 2022
4 bites in 3 daysBull shark Sydney, January 2026
After 126.8 mm of rain on 18 January 2026, four people were bitten or had boards bitten, one fatally in Sydney Harbour. The shark-incident database lists all four as bull sharks. One eventShark-Incident Database · Netweather 2026
Prey moving south
The slower shift: what sharks hunt is changing along the coast.
Kelp gone by 2009Reef fish Coffs Harbour
As the water warmed, tropical fish arrivals rose steadily and some local temperate species declined. From video surveys, 2002–2018. StrongSmith, Vergés et al. 2021
Turtles southTiger shark NSW
Tiger sharks eat sea turtles, and turtles are turning up further south. Researchers expect prey like this to shape where tiger sharks go as much as temperature does. Expert viewABC 2026
Can we see prey moving with the sharks in this page's own data? Not yet. The shark-incident database records the month but not the day of each bite, so it can't be matched to daily rain, and there is no open long-term record of baitfish along this coast to compare with. The tracking studies above are the best evidence. Data that could close the gap: IMOS animal tracking (sharks and fish on the same receivers) and Redmap (sightings of species outside their usual range).
Could something else explain it?
We checked the obvious alternatives.
It isn't more sharks. Oceanic sharks and rays are down about 71% worldwide since 1970, and big sharks in Queensland's nets are down 74–92%.
It isn't only more swimmers. Australia's population has grown more than sixfold since 1900, which helps explain more bites overall. It doesn't explain why bites have moved south, later into the year and into coastal waters.
It isn't one hot spell or El Niño. Unusually hot months don't bring more bites, and El Niño shows no effect on the east coast. What matters is a warm season that lasts.
All seven checks, with sources, are under Researchers.
Staying safe
What actually reduces bites, and why bull sharks are the hard case
Most shark safety tools were designed for white sharks in clear water. Bull sharks bite in murky water, close to shore, and now later in the year.
First, perspective
For every shark death on Australia's coast, about 49 people drown.
July 2015 to June 2025. Each dot is one life.
1,277 coastal drownings26 fatal shark bites
Swim between the red and yellow flags, and pick your time. Lifesavers watch for rips there, the bigger killer. After heavy rain, stay out of harbors and rivers for 72 hours and beaches for 24, and check the SharkSmart app.
Shown to help
Freedom+ SurfTested on 3 species
An electric device for surfboards. Cut bites by 54% across white, tiger and bull sharks in a 2024 test. Against bull sharks alone it cut bait-taking by 42%, but they grew used to it over three weeks. Clarke et al. 2024 · Gauthier et al. 2020
Rpela V2Tested, mixed
A surfboard electric device. Cut white shark bites by about two thirds in 2021 (the first version showed no effect in 2018), but against bull sharks cut bait-taking by only 16%. Blount et al. 2021 · Gauthier et al. 2020
Freedom7, for diversTested, mixed
Cut tiger shark bites by 69% but made no difference for white sharks in the same 2024 study. In 2016 it kept white sharks about 1.3 m away on first approach. Clarke et al. 2024 · Kempster et al. 2016
Listening stations and alertsIn use
37 real-time stations, at least one in every NSW coastal council area and more being added in Sydney Harbour, detect tagged white, bull and tiger sharks and alert the SharkSmart app. They only hear sharks that have been tagged. NSW DPI
Stopping bleeding fastTested first aid
Most shark-bite deaths come from blood loss, often within minutes. In a 2021 trial with healthy volunteers, pressing a fist hard into the groin crease cut blood flow to the leg by about 90%, twice as well as a surfboard leg-rope tourniquet; the technique is not yet in Australian Resuscitation Council guidelines. About 250 community bleeding kits with tourniquets now sit at beaches in NSW and Western Australia (mid-2026), and one was used in June 2026 after a white shark bite at Coogee; the woman survived. Leashes with built-in tourniquets are sold; the tourniquet in one of them passed a 2020 peer-reviewed self-application test, but no study has tested the leash in the surf. In an emergency, call your local emergency number first (000 in Australia, 911 in North America, 112 across Europe and on most mobile phones worldwide). This is research, not first-aid instruction: learn bleeding control from an accredited first-aid course. Taylor et al. 2021 · Canberra Health Services 2022 · Surfer Today on Community Shark Bite Kits, 2026
Helps, with limits
Shark netsOfficial report
In the 2025–26 season, nets at 51 beaches from Newcastle to Wollongong caught 210 animals. Only 36 were target sharks (23 white, 9 tiger, 4 bull); two thirds of all animals caught died, and 48 were threatened species such as grey nurse sharks, turtles and a humpback whale. Since 2024 the nets come out on 31 March, a month earlier, to protect turtles.
Alert a crew when a shark takes the bait so it can be tagged and released offshore. NSW now runs 305 year-round along its coast. In the first south coast trial, all 11 sharks caught were released alive, but none were bull sharks. NSW Government, January 2026 · NSW DPI 2019
DronesIn use, field tests
By late January 2026, NSW lifesaver drones had flown 29,431 flights that season, spotted 461 sharks and supported 170 beach evacuations or alarms. In Queensland’s 2020–24 trial at 10 beaches, drones recorded 676 shark sightings while nets and drumlines at the same beaches caught 284, despite flying only about 3% of the time the nets were set; murky water cut how many sharks drones could see. Their limit is murky water: in tests, almost no shark-shaped targets were seen 2 m down when visibility was under 1.5 m. NSW Government 2026 · Mitchell et al. 2025, Queensland drone trial report · Butcher et al. 2019
Bite-resistant wetsuitsTested, white and tiger
Four bite-resistant materials all cut severe tearing from white and tiger shark bites compared with ordinary 3 mm neoprene, the kind of wound that causes heavy bleeding, with little difference between them. They don’t stop a bite or crushing injuries, haven't been tested with bull sharks, and no study has yet looked at real incidents. Clarke et al. 2025, Wildlife Research
Sonar buoysTrial
Correctly identified white sharks 45% of the time within 46 m. A useful extra layer, but it misses more than half. NSW Shark Management Strategy
Boat-sized electric fieldTested, white sharks
Ocean Guardian BOAT01 is designed to protect an area about 8 by 6 m. In a 2022 test with 43 white sharks it cut bait-taking by up to 48%, but only worked within about 3 m. Riley et al. 2022
No effect found, or not shown
Patterned "shark camouflage" wetsuitsNot shown
Striped or patterned wetsuits are sold to break up a surfer's outline. The only trial we found, with white sharks in 2016, was promoted by the maker and has not been peer reviewed. Sharks are probably colour-blind and see mostly outline, which is why researchers moved to lights: in 2024, light stripes on seal-shaped decoys deterred white sharks, but they haven't been tested on surfers yet. Business News 2016 (sponsored) · Ryan et al. 2021
Magnetic bands and leashesNo effect found
SharkBanz bracelet and leash: no measurable difference to how often white sharks took the bait. Huveneers et al. 2018
Two more surfboard electric devicesNo effect found
E-Shark Force and NoShark did not reduce bait-taking by bull sharks. With E-Shark Force, sharks touched or took the bait 97% of the time, the same as with no device. Gauthier et al. 2020
Electric ankle bandLittle effect
The Electronic Shark Defense System did not reduce how many white sharks came to the bait, and only worked within about 15 cm. Egeberg et al. 2019
Barriers in the surfTrial stopped
Two NSW north coast trials stopped because neither barrier could be installed effectively and safely in ocean surf. NSW Shark Management Strategy
A 2025 review of 67 studies found electric devices the most effective personal option, working mainly within about 2 m, and well-maintained barriers the only measure likely to fully prevent contact. It also found few studies measured actual bites, and there is no standard way to test. No deterrent stops every bite and there is no Australian standard for them, so look for a published, independent test with the shark species found where you swim. 19 Degrees summarises published research; it does not recommend or endorse any product and is not safety, medical or legal advice. Always follow lifesavers, local authorities and beach signs. See all 26 products we checked. Riley, Bradshaw and Huveneers 2025, Marine Policy
Still unknown
Two things the data can't answer yet
White sharkOur data
White sharks are moving the other way
Open
Are more people in the water when sharks are?
Open
Hot days send more people to the beach, and marine heatwaves can push fish and sharks inshore. Both could put more people and sharks in the same shallow water at once, but no study has measured the two together for Australia. It matters, because bites depend on people as much as on sharks.
Five more open questions, from shrinking sharks to acidic water, are under Researchers, with the testable claims, methods and data. Teachers: classroom sheets are under Students and schools.
Looking ahead: what it means
If nothing changes: 2050.
If each beach keeps warming at its pace since 1980, this is what the 19°C line would mean around 2050 for where bull sharks can be, how long they stay, and how often they bite. It extends the trend; it is not a climate model.
Range
Season
Bites
Months a year at 19°C or more, by beach
Now (2016–2025 average)Added by about 2050 at the recent pace
View as a table
What that means for the years ahead
Expect bull sharks off more of the coast, for more of the year. The warm season is already months longer, and bites now come in autumn and winter, not just summer.
Watch the rain. Bull shark risk rises in murky water after heavy rain: wait 72 hours in harbors and rivers and 24 hours at ocean beaches.
The water is still the bigger danger. About 49 people drown on Australia's coast for every shark death. Swim between the red and yellow flags.
Get involved
Spotted something? Help the science.
Log an unusual sighting
Seen a fish, turtle or shark further south than it usually lives? Log it with a photo on Redmap, where scientists check each report and use them to track range shifts.
A real climate story, with real data, for the classroom.
Everything here comes from the same records scientists use. Pick a printable sheet for your class, or use the facts and questions below for a project. Each sheet has teacher notes on its last page: learning intentions, success criteria, big ideas, curriculum links for Australia, the US, England, the International Baccalaureate and others, and the UN Sustainable Development Goals, a lesson sequence, differentiation, a wellbeing note and an answer guide. See all teacher notes.
How warm is the sea at the beach nearest you today? Is it above or below 19°C? (See "Right now" in the story.)
Which months would a bull shark be able to visit Sydney in 1900, and which now?
Why might bites move out of rivers and onto beaches? List three possible reasons and how you could check each.
Why are there fewer oceanic sharks and rays than in 1970, and why does that matter?
Tiger sharks eat sea turtles, and turtles are turning up further south. Could tracking turtles help predict when tiger sharks arrive? What data would you need?
Words to know
Sea surface temperature
How warm the top few meters of the sea are.
The 19°C line
How far south the sea stays at 19°C (66°F) or warmer. No bull shark bite in Australia since 1900 happened in a month when the sea was cooler.
Estuary
Where a river meets the sea, so the water is part fresh, part salty.
Range and season
Range is where an animal can live; season is the part of the year it is there.
Marine heatwave
Days when the sea is much warmer than usual for that place and time of year.
Stay safe: about 49 people drown on Australia's coast for every shark death. Swim between the red and yellow flags.
For researchers
Help test this.
19 Degrees is open: every number here can be checked, and every claim can be challenged. The aim is a shared, growing evidence base on sharks and a warming ocean. Here's how to take part.
1
Test a claim
Fifteen specific claims, each with what would support it and what would rule it out. Pick one that fits your skills.
Think the 19°C rule, the move into coastal waters or a number here is wrong? Show it. Corrections are credited too.
Start in five minutes. A short Python notebook reproduces the two headline results, 0 of 170 bull shark bites below 19°C and the move into coastal waters, from the downloadable data. Download the starter notebook · get the data
Fifteen testable claims
Pick a claim. Say what would prove it wrong. Test it.
Each claim follows from this page but can't be proved by it. Each card says, in advance, what result would support it and what would rule it out, plus the data and who holds it. Good starting points for a student project, a thesis or a grant.
1. Where and when sharks areRange and season
C1RangeEarly result: holds in Queensland
Bull shark catch rates in shark-control gear are rising at the southernmost beaches, not just bites.
Early result (exploratory, not specified in advance): in southern Queensland's shark-control gear (Rainbow Beach to the Gold Coast), bull sharks rose from 6.1% of all sharks caught in 1996–2005 (147 of 2,423) to 12.6% in 2016–2025 (308 of 2,450): a rise of 6.5 percentage points (95% CI 4.9 to 8.1; p < 0.001). In the north their share fell from 18.4% to 14.6% (−3.7 points, 95% CI −5.1 to −2.4). This is share of catch, not catch per unit of effort, which isn't published. NSW data would extend it south. Queensland Shark Control Program data
Supports it if
bull shark catch per net or drumline rises at the southern beaches from the 1990s to now, after allowing for changes in fishing effort.
Rules it out if
catch per unit of effort is flat or falling, or rises equally at northern beaches.
Medical or forensic review · Restricted; needs ethics approval
C10DetectionOpen
Drones with infrared or multi-band cameras spot shark-sized targets in water under 1.5 m visibility at least twice as often as standard drones.
Supports it if
detection rates are at least double in matched murky-water trials.
Rules it out if
the gain is small or none.
Data
Field trials with shark-shaped targets and tagged sharks
Who holds it
NSW DPIRD; Southern Cross University
Skills
Field trials · New fieldwork
C11Bleeding productsOpen
A tourniquet built into a surf leash stops blood flow to the leg as well as a standard medical tourniquet, when an untrained surfer applies it in under a minute.
Already known
A 2020 peer-reviewed study found the OMNA marine tourniquet, the device built into one leash, could be self-applied effectively in all 540 test applications by volunteers, including one-handed. It was a controlled test, not in the surf, and didn't test the leash or a bystander helping someone else. A 2021 trial found an improvised leg-rope tourniquet cut leg blood flow by under half. Hingtgen, Wall and Buising 2020, Journal of Special Operations Medicine · Taylor et al. 2021
Products to test
OMNA tourniquet leash; for comparison, a standard medical tourniquet (such as the CAT) and an improvised leg rope.
Supports it if
blood flow measured by ultrasound stops as completely as with a standard tourniquet, and most first-time users fit it in under 60 seconds, wet and on a board.
Rules it out if
flow is only partly reduced, as with an improvised leg-rope tourniquet, or fitting takes too long.
Data
Volunteer trials like the 2021 groin-compression study: ultrasound flow, time to apply, user errors
Who holds it
Emergency medicine researchers (for example the ANU team behind the 2021 trial); independent of manufacturers
Skills
Clinical trial design · Needs human research ethics approval
C12Beach readinessOpen
Shark-bite victims at beaches with a bleeding kit close by, or a patrol on duty, have bleeding controlled sooner and survive more often.
Already known
No study yet. Kits are new and spreading fast (about 250 by mid-2026), and individual rescues such as Coogee in June 2026 are reported, but nobody has compared outcomes with and without a kit. A 2022 analysis of two centuries of Australian bites found survival was higher on boards than in the water and suggested time to treatment matters, without measuring it. Tucker et al. 2022
Products to test
Community Shark Bite Kits (tourniquets and compression bandages) and lifesaver trauma kits.
Supports it if
time from bite to tourniquet is shorter and survival higher where a kit was within a few minutes' reach or lifesavers were on duty, after allowing for bite severity.
Rules it out if
there's no difference once bite severity and location are accounted for.
Data
Incident reports: time to first aid, kit or patrol present, distance to kit, ambulance arrival, outcome
The beaches gaining warm-water months fastest are among the least prepared: fewer bleeding kits, fewer patrol days and longer ambulance times.
Already known
No study yet. Kit locations are reported council by council in local news; there's no single public map. This page's beach-by-beach warm-season data is ready to join to one. New places matter too: models suggest tiger sharks could reach Tasmania's east coast by 2030, and one was detected at Maria Island for the first time in 20 years of monitoring (Niella et al., reported by ABC 2026).
Supports it if
a map of readiness (kits, patrol days, ambulance response) shows gaps concentrated where this page's warm season is growing fastest, such as the NSW south coast.
Rules it out if
readiness is spread evenly, or best where warming is fastest.
Data
Kit locations, patrolled beaches and seasons, ambulance response times, this page's beach-by-beach warm months
Who holds it
Community Shark Bite Kits; Surf Life Saving (Beachsafe); state ambulance annual reports; 19 Degrees data
Skills
GIS, data joining · Mostly public; kit locations on request
C14WetsuitsOpen
Bite-resistant wetsuits reduce injuries from bull shark bites, not just white and tiger shark bites, and reduce severe bleeding in real incidents.
Already known
Two studies with white sharks (2019) and white and tiger sharks (2025) found bite-resistant fabrics cut punctures and severe tearing compared with neoprene. Neither tested bull sharks or measured injuries to people. Whitmarsh et al. 2019 · Clarke et al. 2025
Products to test
SharkStop, ActionTX-S, Aqua Armour and Brewster bite-resistant fabrics, against ordinary neoprene.
Supports it if
bait trials with bull sharks show the same drop in severe tearing as for white and tiger sharks, and real incidents involving these suits show less severe wounds.
Rules it out if
bull shark bites, which crush as much as cut, do as much damage through the material, or real wounds are no less severe.
Data
Material bite trials with bull sharks; incident reports noting what the person wore and the injury
Who holds it
Flinders University (Huveneers group); Taronga Conservation Society (incident details, on request); manufacturers' sales records
Skills
Field trials; injury classification · New fieldwork; incident details on request
C15Wetsuits and boardsEarly result: works on decoys
Lights that break up a surfer's outline from below, proven on seal-shaped decoys, also reduce white shark approaches to real surfboards, and work for bull and tiger sharks.
Already known
Partly tested. In a 2024 study off Mossel Bay, South Africa, LED lights brighter than the background on the underside of seal-shaped decoys deterred white sharks, and stripes across the direction of travel worked best. It used decoys, not surfboards or people, and only white sharks; the authors say more experiments are needed before it's used to protect people. Ryan et al. 2024, Current Biology
Products to test
Counter-illumination light prototypes; SAMS patterned wetsuits as a comparison.
Supports it if
boards fitted with light stripes are approached and bitten clearly less often than plain boards in blind, independent trials, including with bull and tiger sharks.
Rules it out if
approach rates on boards are the same, or sharks get used to the lights within a session.
Data
Board and decoy trials with white, bull and tiger sharks, recorded on video and scored blind
Who holds it
Macquarie University neurobiology lab (Ryan, Hart); Flinders University
Skills
Field trials, video analysis · New fieldwork; needs animal ethics approval and permits
Data we need
Have data? It could settle a claim.
This page already uses every public source we could find. What's missing sits with agencies, researchers, surf clubs, councils and health services. If you hold any of this, or know who does, it can turn an open claim into an answer. You don't need to send anything first: a description is enough to start.
Shark tracking and catch
Tagging programs, shark-control programs, university labs
Acoustic detections of tagged bull, tiger and white sharks, especially south of Sydney C2 · C5 · C8
Shark-control catch by species, beach and year for NSW and WA C1
Drone and detection trials in murky water C10
Ocean, prey and weather
Fisheries, ocean and climate scientists
Baitfish such as mullet: catch by month and region, over decades C4
Downscaled sea temperature projections to 2050 C3
Turtle tracks and nesting dates; humpback counts C5 · C8
Rescues and first aid
Surf Life Saving, ambulance services, coroners, councils, emergency researchers
De-identified incident timelines: time to first aid, kit or patrol nearby, outcome C9 · C12
Bleeding kit locations, patrolled beaches and seasons, ambulance response times C13
Tourniquet and leash trials C11
Bites and products
Shark researchers, product labs and makers
Evidence that confirms the species in past bites: bite analysis, tooth fragments, DNA, video of the shark All charts
Exact dates and places of bites, to test the rain and river-mouth link C6
Bite trials of wetsuit fabrics and lights with bull and tiger sharks C14 · C15
How sharing works
Tell us what you have. Use the contact form, or open a data offer on GitHub. A short description is enough.
Agree how it's used. Openly under CC BY, summarised only (we publish results, never your raw data), or under your organisation's own data agreement.
Keep people private. Share only de-identified data: no names, contact details, photos of people or medical records that identify anyone. Only share data you have the right to share.
Get credit. Your name or organisation on the claim card and in "What has changed", using the CRediT roles. The data stays yours.
26 products we checked, and what independent tests found
Every shark deterrent, protective wetsuit, bleeding-control product and barrier we could find with a published test, linked to that test. Products sold without any test we could find are left out. Researchers: the untested and partly tested products are where new trials would help most, especially with bull sharks.
Product
Tested with
What tests found
Evidence
Source
Electric deterrents
Ocean Guardian Freedom+ SurfSurfboard
White, tiger, bull
Cut bites 54% across three species (2024); 60% for white sharks (2018); 42% for bull sharks, who got used to it over three weeks (2020).
Listing is not endorsement. Results are from published tests as of October 2026; products may have changed since they were tested. Makers and researchers can send new independent results through the contact form.
Open questions
What scientists still don't know
Some ideas about sharks and climate change are well tested, some rest on a single study, and some are still guesses. Each is marked with how strong the evidence is. Two more, white sharks moving north and people in the water, are in the story.
Strongseveral studies agreeSomeone or two studies, or one regionWeakearly, small or disputedOpennot yet tested
What happens when sharks stop leaving?
Some
Bull sharks already stay longer off Sydney, and pups stay longer in warmer US nurseries. What it means for the places they would normally leave, or arrive in later, has hardly been studied. A longer stay also means more months in which people and sharks share the water, which is the risk this page measures.
Lubitz et al. 2025; Matich et al. 2024
Will big sharks lose out to small ones?
Weak
Some small bottom-dwelling sharks, such as the epaulette shark, can survive very low oxygen and warm tide pools, so some expect them to fare better than big sharks that need lots of food. But even epaulette embryos struggled near 31°C, the summer temperature expected on the Great Barrier Reef by 2100: they developed faster, hatched smaller and had to feed almost immediately. Being small and tough is not a guarantee.
Sharks are cold-blooded or partly warm-blooded, so warmer water speeds up their bodies. Embryos develop faster and use up their energy sooner, so young sharks need more food sooner. Whether that means faster growth, earlier death or more pressure on prey in the wild hasn't been measured.
Wheeler et al. 2021
Does acidic water dull a shark's sense of smell?
Weak
In one lab study, smooth dogfish kept in water with the carbon dioxide expected by 2100 spent under 15% of their time following a food scent, against over 60% for normal water. But it was one small study, larger efforts to repeat similar results in reef fish failed, and the lead author was later found to have committed misconduct on other papers. Treat this as unproven.
Tropical fish are replacing kelp-forest fish on reefs off NSW. Whether local sharks change what they eat, or warm-water sharks moving south take over, hasn't been tested.
Smith, Vergés et al. 2021
Have a question we haven't asked? Good questions become the next testable claim.
Robustness checks
Could something else explain it?
The warming explanation has to survive the other big changes in the ocean and on the beach. Here are the six alternatives people raise most, what we checked, and the verdict.
More sharks in the waterUnlikely
Oceanic sharks and rays fell about 71% worldwide between 1970 and 2018, mainly from fishing, and catch rates of big sharks in Queensland's shark nets fell 74–92% over 50 years. Rising bites near some beaches aren't a sign of more sharks overall. Neither study counts bull sharks separately, so a local rise in bull sharks can't be ruled out; claim C1 tests that. Pacoureau et al. 2021 · Roff et al. 2018
More people in the waterExplains part
Australian Bureau of Statistics
Bites blamed on the wrong sharkFindings hold
Many bites are put down to a species from what a witness saw, which can be wrong. If bites were often blamed on the wrong shark, the patterns could be a mistake rather than a real change. So we re-ran the findings using only bites where the species was confirmed by bite analysis, a tooth, DNA, a photo or video. There are fewer bites, but the proportions barely change, so the pattern holds: Australian Shark-Incident Database
Better reporting todayShares unaffected
Far more bites are reported now than a century ago, which inflates counts. The main findings are shares, the share of bites in water below 19°C and the share in coastal waters, which don't depend on how many bites get reported. They would only shift if reporting improved more for beaches than for rivers, which these records can't check. This page's method
El Niño and La NiñaNo effect on the east coast
Niño 3.4 index from HadISST; Australian Shark-Incident Database
One-off hot spellsNot the driver
In early 2011 the "Ningaloo Niño" heatwave pushed the sea off Western Australia up to 5°C above normal, yet no bull shark bites were recorded there from 2000 to 2014. What matters is a warm season that lasts. CSIRO · this page's data
Whales coming backNot for bull sharks
Humpbacks off eastern Australia recovered from as few as 200–500 in 1962 to about 24,000 by 2015. Whale calves and carcasses feed tiger and white sharks along the migration route, which could bring them near the coast in winter and spring. It doesn't explain bull shark patterns, and hasn't been tested for white or tiger shark bites. Great Barrier Reef Marine Park Authority
What this adds up to. Fewer sharks overall, more people, no help from El Niño on the east coast, and no effect of one-off hot spells, yet a longer warm season and bites moving south, later in the year and into coastal waters. Warming is the explanation that fits all of these together; it doesn't have to be the only cause to be the main one. Claim C1 now adds Queensland's shark-control catches to the picture.
Why other studies find different thresholds. Mobile Bay's 22.5°C comes from a model of where young sharks were caught in a warm bay; this page's 19°C is a monthly average for the open sea offshore, which runs cooler than the harbors and rivers where bull sharks bite. Different places, life stages and measurements give different numbers. What every study finds is that there is a line, and it is moving poleward.
How to contribute
What to send, what gets added, and how you're credited
What to send
The claim ID (C1–C15) or your question.
Your data source and how others can get it.
Your method, and what result would have proved you wrong.
Your result, including if it didn't support the claim.
Code or a notebook, if you have one.
What gets added
Results others can reproduce from data they can access.
Negative results, which matter as much as positive ones.
Work that respects data licenses and privacy. Never contact people who were bitten or their families for this project.
How you're credited
Your name, and a link to your work, on the claim card.
An entry in "What has changed" with the date.
The claim's status updated: supported, not supported or mixed.
Standards every result is held to
Before you start
Write down your hypothesis, data, method and what would prove it wrong before you look at the result. A public pre-registration (for example on OSF) is ideal.
Get the approvals your work needs: human research ethics approval for records about people, such as coroner files, and animal ethics approval and permits for fieldwork with sharks.
Check the data licence allows your use, and cite it.
When you report
Give the effect size with a 95% confidence interval, not just a p-value.
Say how many tests you ran, and label anything you found by exploring rather than planned.
Share code and data, or exactly how to get them, so someone else can reproduce the result.
Disclose funding and any conflict of interest, including links to deterrent makers or advocacy groups.
How a claim's status changes
Open
No result yet.
In progress
Someone has said they're testing it.
Early result
A first, exploratory test. Not yet confirmed.
Supported or not supported
A planned test, reproduced independently from the shared code and data.
Mixed
Credible results point both ways.
Contributions are credited using the CRediT contributor roles. 19 Degrees is not peer reviewed; claims marked supported have been reproduced, not refereed. Results headed for publication should go through a journal.
For teachers, students and scientists
Words, methods and sources
Words used on this page
Sea surface temperature
How warm the top few meters of the sea are. Here it is a monthly average for a 1° square of open sea, about 110 km across.
The 19°C line
How far south the sea stays at 19°C (66°F) or warmer. No bull shark bite in Australia since 1900 happened in a month when the sea was cooler.
Estuary
Where a river meets the sea, so the water is part fresh and part salty. Bull sharks can live in both.
Marine heatwave
A stretch of at least five days when the sea is much warmer than usual for that place and time of year.
Ocean acidification
The sea absorbs carbon dioxide from the air, which makes it slightly more acidic.
Range and season
Range is where a species can live; season is the part of the year it is there.
Statistically significant
Very unlikely to be a fluke of chance. A p-value of 0.002 means that if nothing had really changed, a result this big would turn up by luck only about 2 times in 1,000.
Water temperature at each bite. That month's HadISST sea surface temperature for the 1° square of sea nearest the bite. It is an open-sea monthly average, so it says how warm the season was, not the exact water the person was in.
Seasons. For each beach, the months each year with an average of 19°C or more, from 1900 to the latest month available, counted in July-to-June seasons.
Bite zones. The middle 80% of each species' bites by latitude on the Queensland and NSW coast, in four eras.
Inshore bites. Site type of river or estuary/harbor in the database, or a place name containing harbor, river, creek, lake or estuary.
Western Australia test. A Poisson test of 2020s bull shark bites against the 1900–2019 yearly rate, and a one-sided Fisher exact test of the bull shark share of all WA shark bites, 2000–2019 against 2020 on.
El Niño and La Niña. Each month since 1950 labeled El Niño (index +0.5 or above), La Niña (−0.5 or below) or neutral; bull shark bites per month in each, with a two-sided binomial test of the La Niña share.
2050 look-ahead. Each beach's 1980–2025 warming trend carried 30 years forward from its 2016–2025 average month. A simple extrapolation, not a climate model. The bite scenario holds bites per warm-water month at the 2015-on rate, with an 80% Poisson range.
Limits. Bites are rare, so small numbers swing a lot; reporting and species identification have improved over time; and bites depend on how many people are in the water, which isn't recorded.
The bite records belong to the Australian Shark-Incident Database; please cite it, and HadISST, when you reuse these numbers.
How to cite this pageWhat has changed
28 October 2026. Reader tabs for students, researchers and media; a "Help test this" research hub with fifteen claim cards (C1–C15) and a starter notebook; claim C1 tested with Queensland shark-control catch data (early result); Staying safe rebuilt with 2024–2026 studies, the 2025–26 NSW net report and the Queensland drone trial report; "Not just Australia" redrawn around research from other oceans; licences and a disclaimer added; contact form.
October 2026. Added the move into coastal waters, the evidence-only check, El Niño and La Niña, the global evidence, the 2050 look-ahead, open questions, a research agenda and downloadable data.
Weekly. Bites, sea temperatures and today's readings are refreshed automatically; the date of each refresh is at the bottom of the page.
All sources
Australian Shark-Incident Database, Taronga Conservation Society Australia and Flinders University. zenodo.org/records/18752301
Rayner et al. 2003, HadISST sea surface temperature, UK Met Office, via NOAA ERDDAP; cross-checked with NOAA ERSSTv5.
El Niño index: Niño 3.4 box (5°S–5°N, 170°W–120°W) from HadISST, anomaly against 1991–2020, 3-month running mean, following NOAA's Oceanic Niño Index.
Ridgway 2007, long-term trend and decadal variability of the southward penetration of the East Australian Current, Geophysical Research Letters; summary at Redmap.
Oliver et al. 2017, the unprecedented 2015/16 Tasman Sea marine heatwave, Nature Communications, doi:10.1038/ncomms16101.
Butcher et al. 2019, beach safety: can drones provide a platform for sighting sharks?, Wildlife Research, doi:10.1071/WR18119.
Huveneers et al. 2018, effectiveness of five personal shark-bite deterrents for surfers, PeerJ, doi:10.7717/peerj.5554.
Poloczanska et al. 2013, global imprint of climate change on marine life, Nature Climate Change; summary at University of British Columbia.
Kempster et al. 2016, how close is too close? The effect of a non-lethal electric shark deterrent on white shark behaviour, PLoS ONE; record.
Clarke et al. 2024, personal electric deterrents can reduce shark bites from the three species responsible for the most fatal interactions, Scientific Reports; record.
Gauthier et al. 2020, variable response to electric shark deterrents in bull sharks, Scientific Reports; record.
Blount et al. 2021, effectiveness against white sharks of the Rpela personal shark deterrent device designed for surfers, Journal of Marine Science and Technology; record.
Riley, Bradshaw and Huveneers 2022, ICES Journal of Marine Science; summary.
Taylor et al. 2021, stopping haemorrhage by application of rope tourniquet or inguinal compression (SHARC), Emergency Medicine Australasia; record.
Riley, Bradshaw and Huveneers 2025, systematic review and meta-analysis of studies testing the efficacy of shark-bite mitigation, Marine Policy 184; record.
Clarke, Butcher, Green, Whitelaw, Meyer and Huveneers 2025, bite-resistant wetsuit materials tested with white and tiger sharks, Wildlife Research; record.
NSW Government, January 2026, $4.2 million shark safety expansion (drones, SMART drumlines, listening stations); release.
Mitchell, Scott-Holland, Cross et al. 2025, Queensland SharkSmart Drone Trial (2020–2024) final report, Queensland Government; PDF.
NSW DPIRD, Shark Meshing (Bather Protection) Program 2025/26 and 2024/25 annual performance reports; 2025/26 · 2024/25.
Queensland Department of Primary Industries, Shark Control Program catch data 1996–2026; Queensland Open Data.
Ryan, Hart et al. 2021, juvenile white shark vision and the mistaken-identity hypothesis, Journal of the Royal Society Interface; summary.
Ryan, Gennari, Slip et al. 2024, counterillumination reduces bites by great white sharks, Current Biology 34(24); record.
Whitmarsh et al. 2019, effectiveness of novel fabrics to resist punctures and lacerations from white sharks, PLoS ONE; record.
Hingtgen, Wall and Buising 2020, OMNA marine tourniquet self-application, Journal of Special Operations Medicine; record.
Egeberg et al. 2019, not all electric shark deterrents are made equal, PLoS ONE; record.
The findings, the images, and how to report them accurately.
Free to use with credit to 19 Degrees and the original data sources. Every number below is checked against the data on this page and updates weekly.
Key findings
Story angles
It isn't more sharks
Shark numbers worldwide have fallen sharply, yet bites are moving south, later into the year and into coastal waters. The story is where and when people and sharks now meet.
Western Australia's bull shark jump
More bull shark bites since 2020 than in the previous 120 years combined, very unlikely to be chance. Half were in the tropical north, half around Perth.
Out of the rivers
Bull shark bites used to happen in harbors and rivers. Most now happen in coastal waters, often after heavy rain.
Sydney in 2050
At the pace of warming since 1980, the sea off Sydney would be warm enough for bull sharks almost all year by 2050.
Getting it right
Say "bites," not "attacks." Most bites are investigative or mistaken; researchers and Australian agencies use "bite" or "incident."
It is not "more sharks." Oceanic sharks and rays are down about 71% worldwide since 1970. What has changed is where and when people and sharks overlap.
19°C is a monthly open-sea average, not a reading at the beach on the day. Treat it as a seasonal line, not a daily safety cutoff.
Link, not proof. Warming fits every pattern here, but identification, beach nets, rain and more people in the water also play a part. The page says so.
Expect the obvious questions. Isn't it just more sharks? No: sharks are down worldwide. More people? That explains more bites, not bites moving south and into coastal waters. Misidentified sharks? The findings hold with confirmed bites only. El Niño? No effect on the east coast. The full checks.
Put Australia in context. In 2025 there were 65 confirmed unprovoked shark bites worldwide, close to the 2020–2024 average of 61. Australia had 21, five of them fatal, and the United States 25 (International Shark Attack File).
Keep the perspective. About 49 people drown on Australia's coast for every shark death.
All data as JSON and CSV: see "Researchers," then "Download the data."
Researchers whose work is cited
Bull shark tracking off Sydney: Lubitz and colleagues, James Cook University.
Shark and prey movement in Sydney Harbour, tiger sharks heading south: Niella and colleagues, Macquarie University and IMOS.
White shark tracking in southeast Australia: Gooden and colleagues, Southern Cross University.
The Australian Shark-Incident Database: Taronga Conservation Society Australia and Flinders University.
Shark deterrent testing: Huveneers and colleagues, Flinders University.
Contact
19 Degrees is made by Blake Erickson. For interviews, data questions or corrections, use the contact form.
Get in touch
Questions, corrections, or want to use this?
Teachers, researchers, journalists and anyone who spots an error: send a note and Blake will reply. Under 13? Ask a teacher or parent to send it for you.
