Many Scuba divers are not aware of the Box Jellyfish – They should be!

Box Jellyfish

First I must make clear that the Box Jellyfish is not usually found around coral reefs or where there is a lot of sea plant life. Generally it isn’t found where Scuba divers like to be!

It is found in open coastal waters and particularly in estuaries and river mouths after rains. They avoid rough and deep water moving inshore with rising tides.

Their peak season is the wet season but is also found throughout the year.

A Map of concentrations of Box Jellyfish occurrences

The map above shows the areas of main concentration of the Box Jellyfish, Box Jellyfish of varying types and in turn strength of venom are found around Australia, the Philippines, off the Indonesian Coast, Hawaii, Vietnam, the Caribbean and other tropical areas including off the coast of Africa and the Indian Ocean Islands.

There has been a case of them being seen off the coast of North America in the past few years. Perhaps (and this is my own opinion) climate change is responsible for this?


  • Invertebrate of the class Cubozoa (not a true Jellyfish - Scyphozoa).
  • It eats fish and crustaceans.
  • They breed in late summer, maturing from polyps in early spring
  • Lives for about one year.
  • Weighs about 2kg, 25cm across and has tentacles of up to 3m long.
  • It is preyed on by Turtles mainly.
  • It is transparent and light blue in colour making it very difficult to see.
  • They are vaguely cubed in shape (hence ‘Box Jellyfish’) and have about 15 tentacles hanging from each corner.
  • The Box Jelly fish swims in a pulsating motion pushing water from its body allowing it to reach speeds of up to 2 meters per second.
  • They have groups of three eyes clustered on each of its four sides.
  • Stings of the Box Jellyfish have several very severe consequences, due to its cardio toxic (effect on the heart), neurotoxic (damage to the nerves) and dermatonecrotic (effect on the skin) components.

What is the danger?

This Jellyfish is not very visible in the water, in fact it verges on being invisible.

In the event of extensive contact with its tentacles cardiac arrest is likely to result within minutes.

The statistics vary with numbers of recorded fatalities quoted as being over 5500 deaths. This contrasts with official Australian figures of 68 deaths since 1883.
In the Phillipine Islands there are reports of 20 to 40 deaths PER YEAR as a result of Jellyfish stings.

So what's it all about?

The pain of being stung is excruciating and this in itself is known to send a victim into anaphylactic shock which if the person is in water when that happens, will in all likelihood result in drowning.

Fatal Box Jellyfish stings

In events like this the person stung would have extreme difficulties in getting back to shore.
The tentacles stick tightly to the skin and may continue to release venom if not treated correctly, making things worse.
The stings cause necrosis the flesh literally dies and starts to turn ‘soupy’.

The tendrils will sting even if removed from the body of the Box Jellyfish or if the jellyfish is dead.

The Box Jellyfish venom has evolved in such a way as to, virtually instantly, disable prey such as fish and shrimps otherwise the Box Jellyfish’s delicate tentacles would suffer damage.

The attack or venom sting is activated by a chemical present on the skin of the victim, whether it is a fish or a human, not by touch in itself.
The Box Jellyfish found outside of Australia are commonly of a less dangerous species although their stings are still extremely painful and can result in anaphylactic shock related death. Those in Hawaii regularly to be found on the leeward shores (sheltered from the wind).

It is said to kill more people each year than any other marine animal.

Of the 28 known species, only three can cause death in humans. These live in the Gulf of Mexico, Japan and Australia.

First Aid

First aid for most jellyfish stings begins by pouring large amounts of vinegar over the affected area. This prevents any undischarged nematocysts (stinging cells) on the tentacles from firing more venom into the victim. Vinegar does not decrease pain or diminish the effects of the venom. The tendrils may be removed after soaking with vinegar for about 30 seconds. A towel or gloves should be used to avoid further contact with skin.

Depending on the severity of the case, CPR may well take priority over removal of tentacles and neutralisation of the tentacle venom.

Note: Vinegar is not recommended for bluebottle (Portuguese man-o'-war) stings and may have little effect on Irukandji stings. Bluebottle, Irukandji and Chiropsalmus quadrigata stings have specific treatments recommended

Although commonly recommended in folklore and even some papers on sting treatment, there is no scientific evidence that any of the following substances disable further stinging and in some cases may even worsen the release of venom:

  • Urine
  • Ammonia
  • Meat tenderiser
  • Sodium bicarbonate
  • Boric acid
  • Lemon juice
  • Freshwater
  • Steroid cream
  • Alcohol
  • Cold packs
  • Papaya
  • Hydrogen peroxide
  • Pressure immobilization bandages
  • Methylated spirits
  • Vodka

Often in severe Chironex fleckeri stings cardiac arrest occurs quickly, so cardiopulmonary resuscitation (CPR) can be life saving and takes priority over all other treatment options (including application of vinegar).

Get the patient to a professional health care facility as soon as possible

A box jellyfish antivenom or antivenin is available and is recommended for all but minor stings.

Specific indications include cardio respiratory arrest or cardiac arrhythmias, difficulty with breathing, speech or swallowing, severe pain, extensive skin lesions, or skin lesions in cosmetically important areas such as face, neck, hands and forearms

It has to be said it isn’t always this bad, it depends on how much contact and where the contact was made – the chest has more serious implications than the foot for example.

There appears to be a worldwide increase in Jellyfish as a whole, including the Box Jellyfish.
Apart from the obvious downside of the Box Jellyfish, the population explosions in some instances are creating different problems.
The reasons for the Jellyfish blooms are put down to climate change and the more likely – overfishing decreasing the natural predators of these animals.


As with most issues, prevention is better than cure, in this case certainly a lot easier!

When there have been sightings, don’t enter the water.
There are specific wetsuits available to prevent specifically the Box Jellyfish stings.
Australian lifeguards wear nylon pantyhose on their arms and legs for this purpose.

The Box Jellyfish isn't the only underwater creature to be careful of click here to read about more

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