How Safe Is Samui? - May 2018 Update Including Koh Phangan

Koh Samui 2016. Boy saved with CPR and vinegar after near-fatal box jellyfish sting.

So how safe is Koh Samui? There's been plenty of confusion and panic. Is it OK to swim? How many of these 'killer jellyfish' are there? Where are they? What do they look like? How big is the risk? What do I do if I get stung?

The local authorities, if this is accurate, report of 12 box jellyfish stings around Koh Samui up to October, 2015 including the death of a 20-year old German woman. These stings have occurred at Chaweng, Lamai, Mae Nam, Lipa Noi and on Ang Thong island. Nearby Koh Phangan also reports stings including two fatalities in the past 12 months. 

While there is of course a problem and ignoring signs is plain stupid, there is no need to panic. Be vigilant, ask questions, use common sense, take precautions and heed the warning signs (unlike the couple in the photo below putting themselves at serious risk the day after a death at this beach - if it had been a shark attack fatality and the sign said 'Killer Shark. Very Dangerous' they'd be having that drink in the pool). Also note that day or night, there is always a risk. 

Somewhere in the figure of 500,000 visit Koh Samui every year. The equation could be simplified guessing that if half enter the sea for a swim or snorkel then the risk, based on 12 stings this year, would be around 1 in 15,000. Being killed by a jellyfish? 1 in 180,000. This is not to trivialise the problem as the truth is, that '1' could be you!

We take proper precautions (or should) when riding a motor bike, walking across the street, using a power tool, jumping out of a plane, whatever. So to not be that '1' we wear a helmet and follow the rules, look to the left-right and make sure the road is clear, use protective eyewear and gloves, wear a parachute! Accidents will happen but taking the right precautions will minimise the risk. Click here for Risk Information

The same goes with the threat of being stung by a box jellyfish. If you wear a protective lycra suit when entering the water your chances of being stung are almost nothing. Just about every marine biologist entering tropical seas wears a suit because they know better; they choose life, not a tan. Get the suntan on the sand, wear a suit in the sea. There's plenty of info on this blog about suits. Click here for Box Jellyfish Protective Suits

Carry a cheap bottle of vinegar in your beach bag. If there is a sting, immediately splash the sting area with vinegar. Do not try and remove the tentacles - don't touch them. Use CPR if the victim requires it. After around 30 seconds of splashing vinegar, the tentacle's stinging cells will be de-activated and you can remove them with seawater. Immediately seek medical assistance. Click here for Vinegar Information
Box jellyfish are the deadliest animal on the planet. Their venom is lethal and can kill in minutes. They live in tropical seas throughout South-East Asia and Australia and other parts of the world including Hawaii, The Caribbean, Pacific Islands, Indian Ocean and the Persian Gulf. Stings including deaths have been reported in numerous places in Thailand from the Gulf of Thailand to the Andaman Sea. While Koh Samui is now the focus, the risk is no less great at many other beaches across the country.

Unfortunately, little is known about exactly where box jellyfish are in Thailand or if there is a season where they are more common. Research is minimal. No-one knows for certain about what species of box jellyfish is causing the damage. It is a big one. It has multiple tentacles, is highly toxic and is possibly related to Australia's notorious Chironex Fleckeri. [Postscript: research has increased in the area and it is now known that a deadly as yet un-named species of Chironex box jellyfish lives in Samui waters and is responsible for serious and fatal stings.

So whether it is Chaweng or Lamai beach or anywhere else along the Samui coast, it seems there is box jellyfish habitat. How many are there? No-one knows. What is known is that box jellyfish can swim (not float) at a speed of around 3 knots. They are brainless but have a visual system of navigation (eyes with retinas, lenses, corneas) that guide them past obstacles such as rocks, nets and slow-moving human legs. They are almost completely transparent so very difficult to see in the water even if it is clear. They hunt for small fish and shrimp in very shallow, sandy-bottom water close to the shore. The media often refers to a jellyfish 'attack' but all human stings are accidental. It is unsuspecting people making contact with the jellyfish, not vica-versa. Click here for Box Jellyfish Facts

So is it safe to swim at Koh Samui - or for that matter in other coastal areas of Thailand. The answer is not a simple yes or no. The risk remains no different now than what it was 6 months or 6 years ago. Thousand's of happy holiday makers have come and gone leaving with nothing worse than sunburn. If a sign warning of 'Dangerous Jellyfish' is at one beach and not another does this mean the beach with no sign is safer? No. The sign just tells us what we already know. Somewhere out there are box jellyfish. The temporarily signed beach might have had a recent sting and common sense would say 'stay out of the water' for at least a day or two.   

What is needed is a permanent plan to inform visitors and minimize the risk. Would the German woman killed this week have chosen to swim at night had she been better informed about the risk? And the Koh Phangan deaths - would the Thai woman have done the same, or would the parents of the 5-year old boy let him play in the shallows without a protective suit if they had known? It's hypothetical but at least they would have been better positioned to make a decision. 

Permanent warning and information signs plus vinegar stations strategically placed around the island are the frontline of defence against further pain and tragedy. It works in Australia. Waiting for the storm to blow over and continue as normal until the next serious sting does not. It has not worked and will not work. There are other islands and beaches in Thailand that have implemented box jellyfish safety systems - Phuket, Koh Chang, Koh Mak, Koh Lipe - and their tourist numbers have not gone down. People still enjoy spending time in the sea. They are informed, make a choice and have vinegar right there on the beach just in case. There are reports of success and lives being saved. Click here for Box Jellyfish Safety On Koh Mak    

Koh Samui is at a crossroads. The path forward for this popular resort island is written large on the signs that have been posted with every box jellyfish sting experienced over many years. The local tourism and hospitality operators and the island's authorities have for too long gone in the wrong direction; ignoring expert advice, dismissing damning statistics, failing in their duty of care and hoping the problem would just go away. Well, it hasn't and it won't. Box jellyfish are here to stay and the time to do something about it is now.

UPDATE MAY, 2018: 

In mid-2017, two stinger prevention nets were installed at Koh Samui. One is located at Lamai Beach and the second is installed at Chaweng Beach. At 100m long and 7 metres deep, these nets are prototypes in the testing phase and have not yet been proven to be fully safe. They were to be trialled until late-2017, though they are currently still in place. This is an initiative of Thailand's Marine & Coastal Resources Department (in conjunction with the Koh Samui Municipality and Koh Samui Tourism Association) who have been monitoring the nets' effectiveness. Please observe warning and information signs. 
Link To Article on Jellyfish Prevention Nets

Staff of Thailand's Marine & Coastal Resources Department conduct regular (not sure how regular) sweeps with nets in the shallows of certain popular Samui beaches. Wearing full body lycra stinger suits and rubber gloves as protection, they continue to catch the deadly Chironex-type box jellyfish. There have been reports of multi-tentacle box jellyfish stings requiring hospitalisation throughout the second half of 2017.  

Koh Phangan has experienced severe box jellyfish stings including deaths in recent years. The deadly Chironex species are still being caught during collections by marine biologists and support staff at various locations around the island. Authorities and volunteer locals have responded to this situation and warning signs, vinegar poles with first aid instructions plus vinegar stocked SLS stations are scattered around the island. Many locals have been trained by Thai Health Department & marine services staff. A huge prevention net is located at Haad Rin beach. Note that the vinegar may be coloured with food dye to try and deter idiots from stealing it! 

PLEASE NOTE if you or someone gets a sting:

1. CALL FOR HELP - get someone else to contact the hospital or doctor or ambulance service
2. TREAT THE VICTIM - use CPR if needed to keep the victim alive if not breathing and/or no pulse
3. TREAT THE STING - apply vinegar by pouring on sting area for 30-60 seconds
4. TRANSPORT - get the victim to hospital or the doctor as soon as possible

CLICK HERE - How To Treat A Sting

Camille Lemmens is a diving instructor and long-time resident of Koh Samui. He is a strong advocate for water safety in Thailand and is actively working with the local community and authorities to improve box jellyfish awareness and safety. Check out Camille's Samui Info Blog to get the latest on Box Jellyfish activities including Prevention and Treatment Seminars during 2017.
Link To Camille's Samui Info Blog - Jellyfish Seminars 2017


  1. During what season of the year is the box jellyfish most active?

  2. There is no evidence or research to say what season box jellyfish are more active in Thailand. Stings have occurred throughout the year. Some say that jellyfish in general are more prevalent in the Thai rainy season. The season's for box jellyfish are well-defined in Australia but it doesn't seem to be that clear-cut in Thailand. There is very little money for scientific research of this kind in Thailand - most of the money for box jellyfish goes towards safety. Yes the two are associated but first thing's first as far as the government is concerned - protect people, protect their valuable tourism industry. I guess if the problem continues, which it will, the government will be forced to eventually undertake some meaningful research. In the meantime, presume that this is a year-round risk.

  3. No need to spend money for research. Just ask people who are in or at the sea every day. Surfers, kitesurfers, fishermen, boat captains, tourguides and the like. You will find out, that jellies occur more often at places where rivers enter (and bring wastewater) into the sea. Also rain brings wastewater. Between the monsoon seasons, when the surface layers of the sea seems to move less because it is usually wind less, you will have a higher chance to encounter them. Someone has yet to show me a box jellyfish which was floating around samui waters. From my observation The red brown ones are those which hurt people.these are clearly visible compared to box jf.....

    1. Consulting involved locals is an important part of research and is ongoing. Undertaking scientific research is essential in fully understanding the issue and providing Thailand with the expertise to effectively deal with their dangerous jellyfish and minimise the risk for all water users. There may well be a large number of red brown jellyfish but there are box jellyfish in Samui waters as evidenced by sting events and specimens.

  4. August 2017 i 've been in Samui - Lamai Beach, and me and other russian girl have touch jelly fish with big burns... vinegar and 1 hour in osservation to Bangkok hospital, now i'm adsuming courtison care

    1. Sorry to hear Matteo, hope you're both feeling better. Glad to read that you applied the correct treatment. If you have any photos of your stings (or further details) you can send to the email address in our profile, and perhaps the jellyfish can be identified - it may or may not have been a box jellyfish. Thanks.

    2. One net is installed in front of Ozo hotel in chaweng beach. Bye

    3. OK thanks. So it seems one net is at Lamai and there's also one at Chaweng.

  5. Thank u for this very informative and straight forsard blogg. I planned to go a couple of days to Koh Mak in end november this year (2017) and wrote emails to several Resort owners asking about the Box Jellyfish situation in general and specifically at their beach. The answer? Scilence. No one ansvered my questions. At the same time I could read on different bloggs about people beeing stung ... May I tell u that I cancelled my stay ... I will stay at Koh Chang instead that had no reported stings. I also checked with people there who confirmes: No Box jellyfish attacks on Koh Chang. So make your choice. Be safe OK.


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