The alert was announced late yesterday (Mar 23) by the Department of Marine and Coastal Resources (DMCR), following reports from the Upper Andaman Sea Marine and Coastal Resources Research Center and local officials stationed at the Racha Islands Protected Area Management Centre.
The warning comes under the direction of Deputy Prime Minister and Minister of Natural Resources and Environment Suchart Chomklin, who has instructed agencies to closely monitor marine hazards and issue timely alerts to ensure public and tourist safety.
According to the report, large numbers of venomous jellyfish were found floating and washed ashore along Ao Siam on Koh Racha Yai. Surveys recorded a density of approximately 50 jellyfish per 100 metres along both sides of the bay, with fewer observed in the central section.
Officials said the incident occurred during high tide, a period when such marine hazards are more likely to appear.
Marine biologists identified the species as Pelagia, commonly known as ‘fire jellyfish’, measuring around two to three centimetres in size. Despite their small appearance, the jellyfish can cause burning sensations, painful stings, skin irritation and rashes upon contact.
In response, the DMCR is coordinating with local authorities and tourism operators to implement safety measures, including issuing warnings to visitors and requesting temporary suspension of water activities in affected areas until conditions improve.
Officials have also deployed staff to monitor the situation and prepared emergency response measures, including first aid equipment and assistance for anyone injured.
Safety information and first aid guidance are being disseminated online through the DMCR’s warning platform, with QR codes made available to tourists and operators for easy access.
The department confirmed it will continue to closely monitor conditions and issue further updates as necessary.
The latest alert follows a similar incident reported on Saturday (Mar 21) near Koh Mai Thon, where authorities recorded more than 40 jellyfish per 100 metres during high tide.
In that case, officials also identified the species as Pelagia, with several tourists and boat crew members reporting minor stings and skin irritation after encountering the jellyfish. Most visitors subsequently suspended swimming and other sea activities as a precaution.
Authorities noted that outbreaks of stinging jellyfish are typically linked to tidal conditions and seasonal environmental factors, and urged both tourists and residents to remain vigilant.
Visitors are advised to avoid entering the water if jellyfish are visible or if warning notices are in place. Anyone who suffers a sting should seek immediate first aid and medical attention if symptoms persist.