10 Facts About Box Jellyfish, the Jellyfish That Everyone’s Interested in Now

Grew up watching Spongebob Squarepants and believing that jellyfish are kind and generally harmless in nature?

Image: g33kingout.com

Well newsflash;

Not all are as children-friendly as you would think.

And box jellyfish, in particular, are certainly not to be affiliated with a pineapple under the tree or even anything remotely like it.

Spotted at least four times at various locations around Singapore since March, these tentacled creatures have stung at least two people, inflicting unimaginable pain and purple scars that run the length of the leg.

Image: Facebook (Marine Stewards and Haytham El-Ansary)

And they have been so ‘influential’ in their cause that authorities have since warned people not to swim at Sentosa, Lazarus Island and St John’s Island for at least two weeks, after the jellyfish were first sighted in local waters.

Truly, they are fearsome creatures.

But the question begets:

What exactly are these creatures, and why are they so feared in general?

Without further ado, let’s find out.

1. Box Jellyfish

The name “box jellyfish” is actually an umbrella term for around 50 species of box jellyfish, also known as sea wasps or marine stingers. It gets its name from the shape of its bell, which is in the form of a cuboid.

It appears pale blue and transparent, and if I may, almost beautiful and Instagram-worthy.

Image: Wikimedia Commons

2. Venomous

Of the 50 or so species of box jellyfish, only a few have venom that can prove fatal to humans. One of them happens to be the Australian box jellyfish (or “chironex fleckeri”) which is not only the largest of the class, but also touted to be the most venomous marine animal.

Image: bbmlive.com

It’s believed to have a body size that reaches up to 30cm in diameter and thick, bootlace-like tentacles up to 3-metre long.

Image: Pinterest

3. Location

According to the United States’ National Ocean Service, the lethal varieties are commonly found in the Indo-Pacific region and northern Australia.

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In Singapore, sightings of box jellyfish have been reported in the waters off Palawan Beach, Pulau Seringat, Lazarus Island, Tuas, One Degree 15 Marina Sentosa Cove, Tuas and East Coast Park since March. Maybe they’ve swum over to avoid the coronavirus only to realise we’re much worse here.

4. Extremely Painful

According to Dr Karenne Tun, director of the coastal and marine branch of NParks’ National Biodiversity Centre, a sting from the box jellyfish inflicts extreme pain and can result in severe hypertension (high blood pressure), extreme lower back pain, nausea, cardiac and respiratory arrest.

It can also prove lethal in specific cases.

Apparently, their venom contains toxins that assault the heart, nervous system and skin cells.

Each tentacle is said to have around 5,000 stinging cells, which are activated not by touch, but the existence of a “chemical on the outer layer of its prey” – which is our skin, of course.

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5. Death Tolls

Between 1997 and 2015, 15 cases of harsh stinging by box jellyfish were recorded at Koh Samui and Koh Pha Ngan in Thailand, with six proving fatal.

While the numbers don’t seem daunting…


6. After-effects

After being stung, survivors are liable to experience pain for weeks after, and will often have to live with scars where the tentacles made contact.

In 2010, 10-year-old Australian schoolgirl Rachael Shardlow was catapulted into news headlines, after she survived multiple jellyfish stings in an estuary in Queensland.

Intrinsic scars were visible on her leg after the assault.

Image: ABC TV

Similar, though not as thorough, marks could also be seen on the legs of a woman who expressed that she was stung by a box jellyfish in March 2020.

Image: Facebook (Marine Stewards and Haytham El-Ansary)

7. They Can Swim… Fast

Usual jellies float wherever the current takes them, but box jellyfish are different. Possessing a capability to swim at maximum speeds nearing four knots, they propel themselves through the water with intent and purpose.


That’s about 7.4 kmh. Michael Phelps swims about 9.6 kmh, but an average person like Tan Ah Hock swims at a speed of 3.2 kmh. So unless you’re Joseph School, outswimming a box jellyfish might not be an option.

8. They Can Also See

Box jellyfish also differ from the crowd in the sense that they can actually see: they are equipped with eyes on each side of the box.

According to the US’ National Ocean Service, some of the eyes can be “surprisingly” sophisticated, with a “lens and cornea, an iris that can contract in bright light, and a retina.”

These traits have led researchers to believe that box jellyfish actually actively hunt for prey, in contrast to their fellow jellyfish brethren.

9. Carnivores

Box jellyfish are carnivorous in nature, and commonly hunt prey like fish and shrimp.


They are said to utilise their venom to insta-stun or kill prey, so as to prevent any struggles to escape which can damage its delicate tentacles.

10. Remedy

Unimaginably potent as the box jellyfish’s venom may be, there are still treatments available that help to soothe the pain of a sting.

“If stung by a jellyfish, one should rinse the affected area with seawater or vinegar and not try to remove the tentacles, and seek medical attention immediately,” said NParks’ Dr Tun.

Applying “plenty of vinegar” has also been said to curb any cells that have not emitted venom from doing so.

And peeing on your skin doesn’t help; umerous studies have found that there is no truth to the myth that urine can relieve the pain of jellyfish stings.


One possible reason that pee is often touted as a solution is because urine contains compounds like ammonia and urea, which may be helpful for some stings.

The problem is that your pee contains a lot of a water, which dilutes these substances.

With that said, stay safe and keep a constant lookout, especially if you happen to be around the affiliated areas. Should you spot one, you can call the NParks helpline at 1800 471 7300.

Meanwhile, those who happen to sight the jellyfish at Sentosa can call 1800 726 4377 (or approach a beach patrol officer) for assistance.

Don’t even think of taking a selfie with one. Go buy Photoshop instead.

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