Portuguese man o’ war (bluebottle) in Thailand

Not a true jellyfish but a colony of organisms under a gas float, drifting on the surface and blown ashore by wind. The sting is very painful and can sometimes cause a whole-body reaction. Tentacles of stranded bluebottles still sting.

What it looks like

A translucent blue-violet “bottle” float with a low crest on top. Beneath it hang clusters of blue polyps and long bright-blue tentacles that can coil into spirals.

Size: Float usually 3–15 cm; tentacles can trail for several metres.

Where and when in Thailand

On the Gulf of Thailand side mostly from January to April; on the Andaman coast (Phuket, Krabi, Koh Lanta) from June to November, during the southwest monsoon. Washes up on beaches after strong onshore winds.

Andaman Sea · Gulf of Thailand · Most often: January, February, March, April, June, July, August, September, October, November

The sting

Sharp, burning pain with red lines or chains of spots on the skin. Sometimes chest tightness, breathing difficulty or nausea; reactions can be stronger in children and people with allergies.

First aid

📞 Emergency medical services in Thailand: 1669

Leave the water, remove the tentacles (with tweezers, a towel or fingers) and rinse well with seawater; do not rub. For pain, use hot water around 45 °C (as hot as comfortable, never scalding) for 20–30 minutes, or a cold pack if hot water is not available. Australian guidelines advise against vinegar for bluebottle stings, while Thai services use it; if you are not sure it was a bluebottle, treat it as a box jellyfish sting with vinegar. Call 1669 for breathing difficulty, chest pain or a large sting.

Lookalikes

Blue buttons and by-the-wind sailors are also blue and float on the surface, but they are flat discs, not inflated floats, with short tentacles. Plastic bags and balloons are sometimes mistaken for bluebottles too.

Did you know

• A bluebottle is a siphonophore: a colony of specialised individuals — some catch prey, some digest it, others reproduce.
• It cannot swim; its crest works as a sail.
• Stinging cells stay active in dead and dried-out bluebottles on the beach, so do not touch them and watch children.

Also called: Bluebottle, Man o’ war, Physalia