Jellyfish and Rip Currents at Thai Beaches: Vinegar, Flags

After a jellyfish sting, get out of the sea and call 1669, then pour household vinegar over the sting for at least 30 seconds. Never use fresh water, alcohol or rubbing. Two red flags mean no swimming. The monsoon period runs June to October.

By Vincent Nguyen and team

Get out of the sea and phone 1669. Pour household vinegar over the sting for at least 30 seconds. Do not use fresh water, alcohol or rubbing.

First aid for a jellyfish sting

Follow these steps in order.

1. Get out of the sea at once, ask for help and call the emergency medical service 1669.
2. Keep the injured person still and do not scrub the contact area.
3. Pour household vinegar of 4 to 6% strength over the contact area for at least 30 seconds.
4. If the person does not improve, take them to hospital quickly.

Vinegar stops the stinging cells working but does not relieve pain. Pour it for the full time before trying any other pain relief.

Tentacles and CPR

Remaining tentacles come off with a stick or tongs, after the vinegar. If the person stops breathing or the heart stops, start CPR at once while waiting for transfer to hospital.

What not to pour

Never pour fresh water, white spirit or alcohol, and do not scrub or rub the contact area. It triggers the stinging cells to fire, and more venom enters the body.

Avoid a tight stretch bandage over the stung area. Do not pick up a dead jellyfish with bare hands. Even a stranded jellyfish can still sting, so do not touch it.

For questions, the Department of Disease Control hotline is 1422. Other emergency numbers are on the Thailand emergency numbers page.

Where and when jellyfish are a risk

Jellyfish are found more in the rainy season, especially after rain, in shallow sea or near the shore. Box jellyfish are more commonly seen in the monsoon months, when winds and currents bring them closer to shore.

Box jellyfish are reported occasionally at Ko Lanta, the Phi Phi marine park and Nam Bo Bay in Phuket. Sightings also cover Hua Hin, Cha-am, Ko Tao, Ko Samui, Ko Pha-ngan, Ko Mak and Ko Kut. In August 2026 a 13-year-old died after contact with a box jellyfish at Ban Fai Tha beach in Nakhon Si Thammarat.

Bluebottles on the Gulf coast

The bluebottle outbreak period on the Gulf of Thailand coast is January to March each year. In July 2024 bluebottles were reported at Ao La, Ao Thue and Ko Racha Yai in Phuket.

Ko Samui and Ko Pha-ngan

In January 2020 single bluebottles were found at Lamai and Na Thian beaches on Ko Samui and at Rin beach on Ko Pha-ngan. The Department of Marine and Coastal Resources Gulf research centre heard of them from the local toxic jellyfish network. The Surat Thani governor said these tourist beaches have warning signs and vinegar bottle points.

Fire jellyfish at Phuket beaches

In October 2025 tourists were stung at Patong and Kalim beaches in Phuket, and lifeguards treated them with vinegar; no serious injury or death was reported.

Vinegar points, signs and how to avoid stings

Look for vinegar points and follow warning signs. At Patong the municipality keeps vinegar ready on the beach. The Department of Marine and Coastal Resources has installed vinegar poles with first-aid signs at public beaches in many risk areas.

Wear covering clothing in the water and do not swim after rain. Rash guards, lycra suits or long-sleeved clothing reduce the risk of being stung. If box jellyfish remains lie on the beach, do not swim.

Stop water activities if toxic jellyfish are found or officials warn of them, and do not touch a jellyfish directly. The Department briefs tourism operators before the season in which toxic jellyfish may appear.

Avoid swimming at night, after heavy rain, or outside the buoyed safety zones. The Marine Warning website warning.dmcr.go.th and app carry current warnings.

Beach flags in Thailand

These are the flag meanings the Department of Disease Control publishes for swimmers.

Stay out of the water where red flags fly. Swim in a designated area or where lifeguards are present. Wear a life jacket every time you enter the water or do water activities. Avoid swimming where scooters, banana boats and jet skis operate.

Rip currents: spot them and get out

Rip currents can occur at almost every beach. Two signs show one on the water.

• Water that is whiter and murkier than the water around it.
• Waves that are broken and grooved, with a gap in the wave line on the beach.

If you are caught in a rip current, stay calm and do not swim against it, because you will tire and drown. Swim parallel to the shore, and swim back in once you are out of the current.

Monsoon months on the Andaman coast

The monsoon period runs from June to October, with strong waves. The Thai Meteorological Department marked the start of the 2025 rainy season on May 15, with the southwest monsoon over the Andaman Sea.

In six days from 28 July to 2 August 2023 there were 6 sea drowning incidents, 3 of them in Phuket and one each in Krabi, Rayong and Trang. Eight people died.

For month-by-month beach planning, see best Thai islands by month. Region guides: Phuket, Koh Samui, Krabi and Ao Nang and Hua Hin.

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Not confirmed: The meaning of a purple marine-hazard flag is not confirmed by an official page. Exact box jellyfish season dates by coast are not published on the pages read.

General health information checked against the sources listed above, not medical advice. Rules, vaccine schedules and prices change; see a doctor or the hospital before you act. See how guides are checked.

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