How to Survive an Encounter with a Portuguese Man o’ War?

August 26th, 2010, Sardinia. An elderly woman, obviously distressed, stumbles out from the Mediterranean with a vivid red mark on her right leg. She screams for help, crying she’s been stung, and then collapses on the spot. By the time medics arrive, it is too late. The woman succumbed to anaphylactic shock, an extreme allergic response of the body, narrowing the airways and making blood pressure drop. She had fallen victim to a Portuguese man o’ war. 

A soldier, a ship, or a slimy creature?

To be honest, when I first heard the name Portuguese man o’ war, I envisioned something like this:

men of war

But history and language have their mysterious ways. As eerie as the above story sounds, a few hundred years ago, you would be in much more trouble if you’d encounter a Portuguese man o’ war. At least, if you sailed under Ottoman, Acehnese or Safavid flag. Those were the days of the original Portuguese man o’ war, a huge warship with many cannons, developed in Portugal to fight naval battles in distant oceans and protect its gold-laden armadas on their return journeys home. 

Nowadays, the Portuguese man o’ war is neither a mighty battleship nor a fierce lanceiro, but an odd-looking bunch of jelly-like creatures floating on the water surface. How glorious.

The name comes from a gas bladder, which they use to stay afloat, and kind of resembles a sailing boat. Hence then name. Some even argue it could have reminded sailors of yore of the funny comb-like helmets 15th century Spanish and Portuguese soldiers wore.

You be the judge:

portuguese man of war
helment of a wan or war

With our slippery subject cornered, let’s get to it and find out what the deal is with this physalia physalis, aka bluebottle, floating terror, or Portuguese man o’ war. These funky floaters look like jellyfish, but they’re actually a member of another branch of the cnidarian family (from the Greek word kindē, meaning nettle), to which jellyfish belong, but also anemones, coral and nearly 11,000 other slimy, stingy sea-species. Other than their jellyfish cousins, our man o’ wars are steerlessly free-floating on the surface of all the world’s oceans except the Arctic.

Although a Portuguese man o war appears to be a single organism, it is actually a colony made up of four types of polyps, all needing each other to survive. One polyp is responsible for reproduction, the other deals with the floating business, number three is specialized in catching prey with its long and dangerous tentacles and the last get to eat and digest whatever is fished up with these tentacles, which can get up to 165 feet long in rare cases. Since these guys sometimes float around by the thousands, it’s best for both fish and men to steer clear from man o’ war waters, as contact with these tentacles is no joke.

When are we at risk of encountering a Portuguese man o’ war?

Most people get stung on beaches or on the surface of the water near the shore, as with another Italian woman who was rushed to the hospital in 2022 with severe headache, vomiting, breathing difficulties, panic attacks, cardiac arrhythmia and asthenia beside the signature skin lesions allover her body. She eventually recovered, but it was a close call. 

Not only in Italy, but all over the world, thousands of people are being stung every year, with 10,000 people in Australia alone. Luckily, the vast majority of them don’t end up with the conditions described above. Those make the news because they’re extreme cases. Most people end up in severe pain, but without major life-threatening reactions of the body. 

The culprits of all these painful stings are the many tentacles that extend from the colony. 

The tentacles of a Portuguese man o’ war usually reach up to several meters in length, and may float or dangle below the surface of the water. However, the depth to which they reach depends on a variety of factors, including the size and age of the organism, as well as the strength and direction of the currents. It is possible for the tentacles to be present at depths that are reachable by swimmers or divers, so it is important to be cautious when entering waters where Portuguese man o’ war are known to be present.

What are the odds of encountering one?

It’s hypothesized that the numbers of jellyfish, as well as those of this naughty non-jellyfish, are increasing rapidly due to climate change. Without getting stuck in the equally spiky tentacles of that debate, let’s at least trust the increasing numbers that are being reported each year by beach-goers from Florida to Sardinia and from Australia to, surprise, Portugal. 

portuguese man of war tentacles

Where are we at risk of encountering a Portuguese man o’ war?

Strong winds and currents bring the Portuguese man o’ war to shore. They’re probably as grumpy as you are when you see them on the beach, but what can they do? They’re just floating around enjoying a game of tentacle fishing when they’re suddenly swept up and thrown onto the beach with all their befriended colonies, sometimes in the hundreds. The main thing people don’t realize is that even a dead colony can still cause nasty stings. To be safe, it’s best to keep your distance and even avoid the waters, as more could be drifting around. 

In Portugal, where the species gets its name from, the Portuguese man o’ war is typically more prevalent in the summer months, particularly from June to September, when the water is warmer, and the winds are favorable for them to be carried closer to shore. But the United States’ East Coast gets more of them during Springtime.

Since most people get stung on or near the beach, it’s a good idea to get some info when visiting an unknown beach. If possible, check with local authorities or lifeguards about current conditions and potential hazards before entering the water. 

Another thing to look out for are purple flags along the coast. Members of the International Life Saving Federation all use a purple flag on beaches to indicate dangerous marine life, so if your country’s lifeguards are using these flags, keep an eye out for them. Of course, not seeing any flags doesn’t automatically mean it’s safe.

How dangerous is it to get stung by a Portuguese man o’ war?

Being stung by the nettle-like tentacles of the Portuguese man o’ war will rarely result in death. Unless you’re a crustacean or small fish. It will however leave you with long open wounds or blisters on your skin that may remain forever due to nasty toxins in the stinging cells, called nematocysts.

Are divers at special risk?

If you dive in man o’ war waters without a proper wetsuit on, you could be in for trouble, as the last thing you want is to get stuck in their tentacles while underwater. The Divers Alert Network advises:

  1. Always look up and around while surfacing. Pay special attention during the last 15 to 20 feet of your ascent, since this is the area where you are most likely to encounter cnidarians and their submerged tentacles.
  2. Wear full-body exposure suits regardless of water temperature. Mechanical protection is the best way to prevent stings and rashes. Even thin rash guards or dive skins are usually sufficient to prevent direct contact with most cnidarians.
  3. In areas where these animals are known to be endemic, a hooded vest may be the best way to protect your face, ears and neck.

I would also bring my pet glaucus, a voracious and equally toxic sea slug who eats the Portuguese man o’ war.

Are Portuguese man o’ war aggressive?

Let’s not go overboard about this bunch of floating jelly. It is a colony of organisms that drifts along with ocean currents and has stinging tentacles that can cause painful and potentially dangerous stings if they come into contact with human skin. However, it does not have the ability to actively seek out and attack humans.

These colonies can’t swim and are thus at the mercy of the currents. That means that while they may prefer the open ocean, in certain weather conditions, they can start washing up on the shore and will get close to where humans often swim. 

What to do if you see a Portuguese man o’ war while swimming?

Remember that prevention is key when it comes to avoiding contact with Portuguese man o’ war. Be aware of warning signs and posted advisories at beaches, and if in doubt, stay out of the water.

  1. Get out of the sea
    If you notice a Portuguese man o’ war in the water, try to quickly swim away from it and get out of the water as soon as possible. Do not touch the tentacles or attempt to move the animal.
  2. Tentacle check
    Once you are out of the water, check your body and clothing for any tentacles or nematocysts that may have attached themselves to you.
  3. Alert others
    If you are at a beach or in a public area, alert others to the presence of the Portuguese man o’ war to prevent them from accidentally coming into contact with them.

How to treat Portuguese man o’ war stings?

Although painful, the Man-o-War’s sting generally subsides after 30 minutes, leaving raised red patches on the skin. Some may experience fever and muscle pain. Nausea and vomiting might also occur. In any case, it’s good to reach out for medical help in case more serious symptoms come up.

Traditionally, instant treatments for Portuguese man o’ war stings were practices like scraping off the tentacles and then urinating on the wound or soaking it in seawater. These methods, however, were never properly researched. That’s why scientists from the University of Hawai’i together with their colleagues from Galway, Ireland, did elaborate research and came to the conclusion that all these practices do more harm than good. They could aggravate symptoms to such a level that it can even threaten the lives of victims. According to them, Portuguese man ‘o war stings should be treated no different than jellyfish stings.

Steps to take after being stung by a Portuguese man o’ war

  1. Do not touch!
    Even though the pain may be excruciating, resist going crazy by making wild movements. This will cause the tentacles to roll over unaffected skin, making things worse. 
  2. Out with the needles
    Slowly and carefully, remove the tentacles with gloves or tweezers. If nothing suitable seems to be available, use your fingers and treat them afterward.
  3. Bring the vinegar!
    Luckily, you had a big bottle of vinegar laying by your beach towel! In the unlikely event you didn’t, see if you can get your hands on it, as it will make a huge difference. Rinse the whole area with vinegar, not with seawater. Otherwise, go for the hot water of step 4.
  4. Apply heat
    Heat lessens the pain and inactivates toxins. Therefore, immerse the affected area in hot water between 110 and 113 °F. A hot pack could also be used for about 45 minutes. If no thermometer is around, a rule of thumb is to use the hottest water you can tolerate when you submerge your fingers. The application of heat can be repeated. Don’t go for ice packs. It makes stings worse! 
  5. To the doc
    You’re probably in enough pain to readily accept going to a doctor. In any case, it’s worth to have a check-up, in case more serious symptoms pop up. Good news about not having gone with the urine method is that you save yourself the embarrassment of telling the doctor you just peed all over yourself!

Are there commercially available products against Portuguese man o’ war stings?

Another way to treat the pain and swelling is by taking some Oral antihistamines containing diphenhydramine, or, even fancier, a commercially available sting-relief spray, which was developed especially for dealing with Portuguese man o’ war stings.


All over the world, thousands of people get stung by the Portuguese man o’ war every year, and in most cases the burning pain will subside within a few hours. Still, there are more serious cases, and the pain is a nasty one, making you want to tread with care around unknown or unguarded beaches.

Fortunately, the treatment of a sting is fairly uncomplicated and straightforward, so as long as your pet glaucus is on your side, you don’t have too much to worry about!

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