Box jellyfish: a real but manageable risk

This record is about safety, not fear. Box jellyfish (including the highly venomous Chironex type) are present in the Gulf of Thailand, and Samui has recorded more incidents than its neighbours - stings concentrate at Chaweng, Bophut, and Lamai, mostly in the rainy season and calm-warm periods, roughly June to December. Thai researchers documented 10 deaths and 36 severe injuries nationwide between 1999 and 2021; in 2025-2026 there were further serious stings and at least one child fatality near Samui. Authorities have responded: warning signs and vinegar stations stand at main beaches, and stinger nets were installed at Chaweng and Lamai (net status changes, so check locally). The response protocol matters: if stung, flood the area with vinegar for at least 30 seconds, never use fresh water or rub, remove tentacles carefully, and get emergency help - call 1669. Prevention: heed signs and flags, avoid swimming at night or after storms, consider a lycra stinger suit in the wet months, and keep children in netted areas. Respecting jellyfish warnings is also respect for a shared sea - these animals belong here.

Dates

Risk highest roughly June-December; incidents documented through 2026

Highlights

• Box jellyfish present around Samui; most stings June-December
• Vinegar stations and warning signs at main beaches; nets at some beaches
• Sting first aid: vinegar 30+ seconds, never fresh water, call 1669
• Never touch jellyfish - even dead ones on the sand can sting

Local tips

• Locate the vinegar station when you arrive at a beach - before you swim
• Avoid night swimming and swimming after storms in the wet season

Frequently asked questions

Are there dangerous jellyfish on Koh Samui?

Yes - box jellyfish occur, mainly in the rainy season (about June-December). Fatalities are rare but real, so follow warning signs and use protected swimming areas.

What do I do if someone is stung?

Pour vinegar on the sting for at least 30 seconds (never fresh water), do not rub, remove tentacles carefully, and call 1669 for emergency help immediately.