One of the most fierce creatures on earth is the northern Australian box jellyfish or sea wasp (Chironex fleckeri), which has killed over 70 people since 1883. They might not always appear to be threatening, but the venom of a box jellyfish can send you to the emergency chamber if you’re fortunate and to ICU if you run out of luck.

Red Jellyfish
Red Jellyfish | Image Credit – Blue Ox Studio

Humans and animals smacked by this toxin may undergo paralysis, cardiac arrest, and even death within minutes of being stung. The box jellyfish toxin is one of the most lethal on the planet, comprising chemicals that target the circulatory system, nervous system, and skin cells. 

The Irukandji box jellyfish, which is only 2 inches long, transfer toxins 100 times more potent than a cobra’s bite. But don’t choose a swimming pool over the blue oceans yet! Only around few in a 50 species of box jellyfish, also known as sea wasps, have poison that is dangerous to humans. So what is it about this critter that makes it so lethal? How are you going to avoid it? And what should you do if you are stung by a box jellyfish? Continue reading to find out!

Table of Contents


The term “box jellyfish” refers to the class Cubozoa, containing various species. As a matter of fact, the term “box jellyfish” can refer to multiple separate species. Experts have currently identified around 51 different species in this cluster.


Despite their diversity, fellows of the box jellyfish cluster share various qualities. One distinguishing feature is the structure of their bell, which is the upper section of the jellyfish in which the tentacles are connected. Box jellyfish possess a square bell that gives them their identity. 

A few species possess only four tentacles, while others have many; however, the position at which tentacles adhere to the bell is the same across all box jellyfish. As many as 15 tentacles can develop from each edge of the bell and attain a length of 10 feet. 

Each tentacle contains approximately 5,000 stinger cells. Box jellies are flexible and energetic swimmers with bodies molded nearly like a square bell with tentacles protruding from the edges. This flexibility is due to their capacity to contract the bell and assertively eject water through a cramped entrance at its bottom. 

The box jellyfish class also has eyes, whereas any other type of jellyfish lack sight. They can perceive image data, light, and shadow, which aids in detecting prey and avoiding predators. Box jellies are crucial aspects of ocean life, seizing and consuming fish, crustaceans, and worms and being devoured by large fish and sea turtles, notwithstanding their lacerating and harmed nematocysts.

Feeding and diet

Transparent Jellyfish Swimming on Water
Transparent Jellyfish Swimming on Water | Image Credit – Israel Fernández

They can be found inshore during the warmer months, feeding on harbor-dwelling shrimps, coastline marshes fish, and tributaries prawns. They typically wander into the shallows on humid, gloomy, quiet days in quest of meals. And this sadly can result in stings in muddy coastline stream water during the midsummer rainy season.


Although the distributions of particular species vary, the most deadly species are found primarily in the Indo-Pacific, particularly around Australia, Indonesia, and the nearby islands. We can also find different varieties in the Atlantic Ocean. These species can be found in almost any tropical or subtropical ocean.

The various species in this category exist in multiple environments—each box jellyfish with its specific inclinations. Marine, or saltwater, ecosystems are home to all different species. The majority of animals like to live along the water’s edge. Reefs, beaches, marshes, and other habitats are just some of the places they call home.

Box Jellyfish Actively Hunt Prey

White and Purple Tentacles of a Jellyfish
White and Purple Tentacles of a Jellyfish | Image Credit – Israel Fernández

Box jellyfish are an unusual species. They have twentyfour eyeballs, most of which are equipped with lenses, corneas, and irises for starters. To put it intriguingly, they can see and strike! Nevertheless, a typical box jellyfish’s physiology only permits them to discern between light and dark. 

Box jellyfish have a more complex neurological system than their relatives, enabling them to escape and interact with items more swiftly. The worst thing is that, unlike other jellyfish species, box jellyfish swim while aggressively hunting their target, consisting primarily of prawns and tiny fish. They move through the ocean at a speed of 4 mph by opening and closing their bell-shaped tops, much like an umbrella during a downpour.

The ruthless stings!

Two Men Crouching on Beach Shoreline
Two Men Crouching on Beach Shoreline | Image Credit – Alistair McLellan

The stings of these critters are infamous for being severe and life-threatening.

  • Stings with lethal toxicity – The stings of several distinct species contain deadly toxins. Extreme stings had sometimes led to death when they remained unattended. Experts in Australia have identified at least 64 deaths caused by the sea wasp in the last century.
  • Irukandji Syndrome – Certain species, mainly Irukandji, cause severe symptoms when stung. Anxiety, headaches, nausea, backaches, chest pain, elevated blood pressure, and other symptoms can occur.
  • Trigger warning: These critters’ stinging cells do not ignite when in contact with an item. Instead, they respond to the molecules on the surface of the skin. This response saves the organism’s energy by preventing them from squandering resources on nonliving objects.

Just like a rattlesnake, the box jellyfish do not shoot toxins. When a box jellyfish strikes, it produces a digestive cocktail that aids the organism in catching and digesting its prey. However, this digestion mixture functions as molecular buckshot leading to lesions in all human cells. In as little as five minutes, a human’s heart can stop beating.

Over 5567 people have died due to their deadly sting since 1884. Although box jellies can be extremely harmful to swimmers, divers, and surfers, their unusual appearance and habit enhance the beauty and complexity of our environment.

What Happens If You Get Stung?

You will immediately know if this scariest box jellyfish has attacked you. In truth, several people are taken aback by the sting’s discomfort before any more dangerous symptoms appear. Assuming you don’t go into shock, you may experience various symptoms. If you are lucky, less fatal signs comprise welts and blisters growing on the stung region within seconds, extreme pain, and fainting. 

If the blisters are longer than 700mm, the sufferer is likely to die between 5 and 20 minutes after being injured. Paralysis, cardiac arrest, arrhythmias, fainting, and breathing difficulties are more dangerous symptoms. Initially, the jellyfish stinging looks like a mosquito bite, but symptoms occur within a short period, typically between 5 and 45 minutes. Extreme back pain, headaches, shooting pains throughout the body, dizziness, and difficulty breathing are among the complaints. It is critical to reflect that not all interactions with box jellyfish are fatal. Nevertheless, the stings of the worst jellyfish kill about 100 people yearly.

What to do if you get stung?

Get a medical support
Get a medical support | Image Credit – Cottonbro

You probably wouldn’t be able to do anything to aid yourself if you get struck by a box jellyfish because of the degree of suffering. Immediately ask for assistance in getting out of the ocean and consult a doctor. Meanwhile, rest until you can seek professional support. If you come across someone who a box jellyfish have injured, there are certain things you can do to aid. Firstly, ensure that the stung person is out of the waters. Eliminate any visible stinging cells with covered fingers or forceps.

After that, use vinegar to clean the wound thoroughly. If you don’t have any vinegar on hand, clean the wound with salt water. Make sure not to use freshwater or alcohol. Make doubly sure that someone contacts medical support while you are going through these processes. If possible, hire a lifeguard to assist in keeping the victim calm, particularly if CPR is required.

How to protect yourself from Box Jellyfish stings?

Slim female diver in flippers swimming in blue sea
Slim female diver in flippers swimming in blue sea | Image Credit – 7inchs
  • Throughout the notorious jellyfish period (between September to March), minimize swimming in regions where Box jellyfish can be spotted and pay attention to cautionary notices on coastlines. Diving alone or at seashores is not recommended.
  • When around Box jellyfish areas, use custom-made stinger suits.
  • Swim at locations with lifeguards on duty, mainly equipped with vinegar, antivenom, and rudimentary emergency equipment.
  • When swimming in the sea, use precautions and avoid diving or running into the water carefree.
  • One should closely supervise children because they are more vulnerable to strikes and have lower body weight, increasing vulnerability to venom symptoms.
  • Box jellyfish are not present in locations that have been fenced or netted.
  • To escape the stinging of this species, numerous swimmers wear stockings while plunging or surfing. Since the material acts as a barrier between the water and skin, the stockings prevent the stinging cells from activating.

To Wrap Up

Box jellyfish are one of the world’s most historic organisms, which trace their roots back 600 million years and have survived multiple catastrophic extinctions. The population of box jellyfish, like that of other jellyfish, is increasing, accentuated by warmer waters and oxygen-depleting chemicals that wind up in water bodies. While they are tough to avoid, it is advisable to recognize the signs of a box jellyfish sting if you or somebody gets stung by the organism.

(Last Updated on May 22, 2022 by Sadrish Dabadi)

Shradha Bhatta holds a Bachelors’s Degree in Social Work along with a Post-graduate degree in Project Management from Georgian College in Canada. Shradha enjoys writing on a variety of topics and takes pleasure in discovering new ideas. She likes traveling and spending time with nature. She is a very people-person who loves talking about climate change and alerting people to go green!