Tourists and Aussies alike are being warned about deadly Box Jellyfish arriving in new Australia waters, as they migrate South even as far as Sydney.  The threat of this impending doom is real as Box Jellyfish can kill humans in under five minutes.

These extremely dangerous jellyfish species which have venomous stingers, may force a fashion change, making people think twice about wearing budgie smugglers and revealing bikinis! 


1. Is it possible Box Jellyfish will reach Sydney?

Box Jellyfish | National Geographic

Box Jellyfish are very common during summer months around the top end of Australia but as climate change increases the ocean’s temperatures the currents are being altered.  This means that there is a chance that Box jellyfish could find their way down south to Sydney, as they are very fast swimmers.

Irukandji jellyfish: Diver stung by highly venomous 'stinger' speaks as  national hotspot emerges, 'Waves of pain'

How far south and which new territory they swim will depend on how warm waters become and if temperatures of the ocean get high enough, they could reach Sydney.

It is not yet clear how far their new territory extends as they migrate into new waters. Changes in numbers in other warm water dwelling sea creatures have been observed by extraordinarily increased numbers of venomous dragon sea slugs have been observed on the Gold Coast, Newcastle, Bondi Beach, and Kurnell. Subtropical and tropical fish species are increasing in numbers and thriving through the colder months in Sydney’s Harbour kelp beds. 

2. Which species of Box Jellyfish are on the move to South Australia?

Pain researchers find antidote to deadly box jellyfish sting - The  University of Sydney

There are 49 species of Box Jellyfish of which Australia most often sees species of Chironex Fleckeri and Irukandi. 

The Chironex fleckeri, is the most common killer Australian box jellyfish, (sea wasp, aka stinger) and are found across the northern part of Australia, but they too are on the move south.

Considered as the most venomous marine animal the Chironex fleckeri is the largest of the box jellyfish, with the body sizes reaching up to 30cm and thick tentacles below it extending to about 3 metres. The Chironex fleckeri has up to 15 tentacles coming from each corner.

Global warming could mean more stingers, scientist warns | Daily Telegraph

The Irukandi has four tentacles, one on each corner. 

Urgent warning over 'deadly' Irukandji issued after multiple Broome stings  | Broome Advertiser

3. Have there been any recent sightings of Box Jellyfish near Sydney?

Box jellyfish found off Sydney's Cronulla Beach investigated by scientists  - ABC News

There has been scattered sightings of deadly Box Jellyfish in NSW over the past few decades but until this year no jellyfish had been captured.

Box jellyfish found off Sydney's Cronulla Beach investigated by scientists  - ABC News

Recently sightings of the box jellyfish outside tropical waters in Cronulla both in May 2022 and around the same time in this year, have led to one being captured. Scientists at the Australian Museum are working to identify the marine animal and say it has features of both the lethal and non-lethal varieties.

This jellyfish has several tentacles around 30cm long and is related to the deadly Australian box jelly, Chironex fleckeri. However, the tentacles are unlike the dangerous ones as they are thick, and the deadly ones have thin tentacles. Also there are little gelatinous knobs on the inside of the body which resemble those of non-dangerous species.

Dangerous Jellyfish Found In Lake Macquarie | Triple M

A different Box Jellyfish called the morbakka fenneri was found in the Lake Macquarie area in 2018. These jellyfish are normally found near Brisbane and have unusually travelled south. The morbakka’s sting does produces a reaction known as Irukandji syndrome, which includes lower back pain, difficulty breathing, and in severe cases respiratory failure or a stroke.

Some minute Irukandji species which are only 2cm in diameter have tentacles up to 35cm long. Box Jellyfish have up to 60 tentacles all with millions of injection harpoons filled with venom.

4. Why are box jellyfish dangerous?

Smithsonian Insider – “Ohboya!” It's the Bonaire banded box jellyfish, a  new species | Smithsonian Insider

They have been the cause of a great many deaths in Australia. Most of those are from heart attacks after a sting or drowning after being stung.

When they can’t avoid and object which may be a person, they will brush their tentacles against it. These hundreds of stinger cells (nematocysts) on their tentacles are like tiny darts filled with venom and as soon as they touch the skin, they will push the stinger cells in. Each box jellyfish carries enough venom to kill more than 60 humans. 

How to Survive a Box Jellyfish Sting (According to Science)

A single sting to a human will cause necrosis, were patches of the 

skin dies. Depending on how much surface is brushed against, there may be hundreds of these stings. The venom causes the cells to leak with potassium going into the blood stream. The victim will have excruciating pain and if the dose of venom is large enough it will cause cardiac arrest and death within minutes.

CRISPR Used to Create An Antidote for Box Jellyfish Venom

Other symptoms from a tiny dose of venom from stings include anxiety, vomiting, pain, difficulty breathing. Anyone who is stung by a box jellyfish should get out of the water and seek immediate treatment by finding a lifeguard or calling triple zero.  Vinegar can be used to ease the pain. 

Should you apply vinegar to all jellyfish stings? | Better Homes and Gardens

5. Are there any other new species of Box Jellyfish that  could invade Australia?

Species New to Science: [Cnidaria • 2023] Tripedalia maipoensis • A New  Species of Box Jellyfish (Tripedaliidae: Tripedalia) from Hong Kong, China

Just when you thought that all the deadly jellyfish had been discovered, a new species of deadly jellyfish has been found. This NEW deadly cousin to the Box Jellyfish, Tripedalia maipoens is a highly venomous box jellyfish, and so far, only been discovered in Hong Kong. The jellyfish is distinguished by the formation of internal canals which run along the box margins.

This new species has a transparent and colourless body and 24 eyes! The body is 1.5cm long with three tentacles coming from each corner of its four corners. These tentacles are up to 10cm long covered in stinging cells.

Mystery box jellyfish spotted in Sydney waters may be an entirely new  species, expert says | Sydney | The Guardian

Mystery Box Jellyfish have been spotted in Sydney waters near Cronulla’s Shark Island. and may be a new species entirely.

6. Why are Box Jellyfish fast swimmers?

The Box Jellyfish: Australia's Other Marine Killer — Journal of Young  Investigators

Box jellyfish are fast swimmers due to them having tentacles which are like boat paddles.  This flat pedal-shaped structure, at the base of each tentacle allows the jellyfish to produce strong thrusts when they contract their bodies. This speed helps them catch their fast-swimming prey namely shrimp. Box jellyfish can swim at maximum speeds of up to 4km per hour compared to other jellyfish which float and have little control over their direction. 

Box jellyfish has six eye clusters. Each contains four very simple eyes  consisting of pigment-filled pits to catch light, and a pair of more  complex, lensed eyes. They can't see white or

Box jellyfish have clusters of eyes on each side of the box allowing them to see. Their speed and vision are believed to enable the box jellyfish to hunt their prey, mainly small fish, and shrimp.

7. How can you protect yourself against Box Jellyfish?

Protective clothing such as a neoprene or a full body lycra suit, will provide a shield for the parts on the body where stings occur. The more skin they cover the greater the protection. Stinger suits are full-body suits designed to protect the body from the stings of dangerous jellyfish. They are much lighter than wetsuits, and a suited to the tropical waters. The suits have been engineered to prevent jellyfish tentacles from gripping to the body.

A lotion with a jellyfish repellent can also be applied to the skin before heading out to the water. These repellents work by tricking the jellyfish into thinking the wearer is also a jellyfish which prevents them from stinging in defence.

For Swimmers: The Complete Guide to Jellyfish | Jellyfish Repellent Guide

Wearing waterproof sandals or shoes when walking through shallow water and avoid touching dead jellyfish that have washed up on shore.

Swim with caution especially during jellyfish season and know how to spot a jellyfish. You can recognize a jellyfish by its tentacles floating on the water. Jellyfish can be small or big, clear, or colourful. Box Jellyfish have a clear, ‘Box’

Jellyfish sting victim survival rate may be increased with new finding -  YouTube

8. Are Stinger Nets effective on beaches?

Cairns stinger nets to be removed from Port Douglas to Mission Beach | The  Cairns Post

Marine stinger nets were developed in North Queensland to protect ocean swimmers as they acted as a physical deterrent and barrier to Box Jellyfish and other large marine creatures.

A group of people fishing in the water

Description automatically generated with low confidence

Stinger nets or stinger enclosures are effective at preventing the more dangerous Box Jellyfish from entering the enclosure. Researchers have data to show that Box Jellyfish stings have dropped significantly since stinger nets have been introduced.

Box jellyfish deaths have dropped significantly in North Queensland region where stinger nets are used, compared to the Northern Territory. However, stinger nets cannot guarantee to prevent the much smaller Irukandji jellyfish from entering the enclosure. They are less dangerous than the Box Jellyfish.

stinger nets Airlie Beach | The Courier Mail

It is important to remember that although the stinger nets are effective the nets cannot stop every sting, so swimmers are encouraged to take extra measures. 

9. What conditions allow Box Jellyfish to thrive?

Transparent & Deadly: 7 Facts About The Australian Box Jellyfish

Box Jellyfish thrive in tropical waters favouring warm clear water. They are found in summer months in inshore waters of mangroves, creeks, and rivers, as they feed on prawns, small fish, and crustaceans. 

Box Jellyfish Sting, Size, Habitat, Diet | Chironex Fleckeri

Their eggs once fertilised grow into free swimming larva and settle on rocks in creeks where they metamorphose to feature their stinging tentacles. Small jellyfish then make their way to the ocean.

Researchers have found that the jellyfish swim towards the shore to spawn, on nights in the moon’s cycle when there is a particularly long period between twilight and moonrise The Box Jellyfish consistently appears near the shore 8-10 days after a full moon.

10. How are people warned about the presence of Box Jellyfish?

Stinger Season Begins as NT Teenager Survives Irukandji Jellyfish Sting -  YouTube

Stingers are found in the oceans of tropical Australia all year round, but between the months of October to May are when they are at their highest numbers. This is known as “Stinger Season”.

Jellyfish in Hawaii - Box Jellyfish, Portuguese Man O'War, Sea Lice

Australian authorities post signs on beaches with local warnings for stingers presence.

While stings are most commonly recorded from November - April, they have been recorded at all months in the year.

The best way to avoid stingers is not to get in the water during peak stinger season. Australian authorities post signs on beaches with local warnings for stingers presence.

If you do swim, the last thing you want during swimming is to get stung by a box jellyfish, so precautionary measures are needed to stay on the safe side.

  • Do not swim in Stinger season without a swimming suit or outside swimming enclosures.
  • On lifeguard patrolled beaches the authorities have installed flags and the point beyond whether Jellyfish are likely to occur, swim inside the flags.
  • It is best to swim on beaches which have stinger nets, but this is not an absolute assurance.
  • Never sit on stinger nets
  • If a marine stinger has been washed up on a beach, do not touch it as it can still sting.
Townsville woman stung by box jellyfish at Pallarenda Beach | —  Australia's leading news site
  • Always take vinegar with you to apply if you are stung. 
  • Try to move slowly into the water because marine stingers swim away as you go in.
Irukandji jellyfish: Everything you need to know - Australian ...

Box jellyfish have venom in their tentacles that can sting and kill an adult person in under five minutes. Children are also at greater risk because of their smaller body mass Since 1975 there have been at least 14 deaths in the top end of Australia, all children!. 

On average 50-100 people each year are hospitalised in Australia after being stung by Irukandji jellyfish.

NT boy, 3, survives deadly box jellyfish stings in Nhulunbuy | NT News