Oct 07 2015

The Deadliest Jellyfish in the World


A 20-year old German tourist named Thies Saskia was enjoying a beautiful evening of swimming off the coast of Koh Samui, Thailand, when things took a fatal turn. She got entangled in the long poisonous tentacles of a box jellyfish that had been lurking in the water nearby. After being horribly stung multiple times, the woman died from the extremely toxic venom in her system. Her friend was stung on the hand as well, but survived. Thies Saskia’s death was the 3rd reported fatality caused by a box jellyfish in Thailand in the last 14 months.

A Thai woman and a 5 year old French boy were also killed by the world’s deadliest jellyfish off of another Thai island coast within the same period of time.

Following these incidents, Thai police urged business owners to post signs warning people to beware the jellies in the water to help avoid future casualties.

deadly box jellyfish

In the past 7 years the number of box jellies in Thailand has increased dramatically due to several factors including global warming, food waste from the shore drawing them in to more shallow waters, and a decline in numbers of their natural predators (sea turtles).

A lot of newer warnings advise against swimming at night. These jellyfish are harder to see because they swim deeper in the water rather than floating on the surface.

Some box jellyfish have trailing tentacles that can grow as long as 10 feet, which can deliver stings so excruciating that they can cause victims to instantly go into shock and drown before the venom can even take effect. The few who are lucky enough to make it out of the water after being stung often die a short while later due to the poison in their veins. The toxins can kill someone in as little as 5 minutes. It breaches the bloodstream faster because the tentacles have thousands of stingers that are able to inject their venom over a larger area of skin.

box jellyfish 2



More of the Deadliest Jellies on the Planet

4. The Cannonball Jellyfish

Cannonballs don’t usually sting humans, but when they do the results can do quite a bit of damage. Their toxins often cause cardiac problems such as irregular heart rhythms.

cannonball jellyfish deadly

3. The Lion’s Man Jellyfish

These toxic stingers can paralyze your muscles, leading to cardiac arrest or suffocation. Lion’s Mane jellies can grow stingers up to 10 feet long with thousands of stinging cells that blister the skin and cause paralysis.

lions mane jellyfish

2. The Portuguese Man’O’War

This carnivorous jelly is really a colony of codependent organisms that trap and paralyze victims with venomous tentacles. They also use a process called bio-luminescence to make their tentacles glow in order to lure their prey. Their venom has a tendency to travel into lymph nodes, causing intense pain. The tentacles leave angry red welts on the skin when stung. A lot of children have been stung on beaches because they mistook a Man’O’War for balloons or plastic bags.

Portuguese Man-O-War jellyfish

  1. The Irukandji Jellyfish

Don’t make the mistake of underestimating this jelly just because of its tiny size. Though the Irukandji is hardly the size of a peanut, its venom can cause heart problems and heighten your blood pressure as well as causing other complications. These creatures can be hard to spot in the water because of their clear transparency. They are related to the lethal box jellyfish.

Irukandji tiny jellyfish