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Jellyfish clusters at beaches in Jeju prompt concern from vacationers

Published: 28 Jul. 2025, 19:44

A swarm of jellyfish appears on a beach in Jeju. The bright blue creatures are identified as Porpita umbrella. [SCREEN CAPTURE]

Clusters of bright blue jellyfish have recently washed up on beaches in Jeju, sparking concern among vacationers during the peak summer season. The jellyfish have been identified as Porpita umbrella.

Large swarms of the jellyfish were spotted along popular beaches in Jeju City, including in Sinheung, Hamdeok and Gimnyeong, according to videos and posts circulating on social media Monday. Some users warned that “jellyfish are covering not only the sea but also the sand” and noted that “though they are mildly venomous, they could pose a danger to children.”

The jellyfish have a vivid blue, button-shaped appearance and measure 3 to 4 centimeters (1.18 to 1.57 inches) in diameter. Dozens of tentacles extend from their body, which they use to catch prey. Due to their mold-like appearance, they are sometimes nicknamed the “mold jellyfish.” Contact with the tentacles may cause skin irritation, prompting authorities to urge caution.

Typically found in warmer waters such as the Pacific Ocean, Mediterranean Sea and Indian Ocean, the species can drift into Korean waters under specific conditions, such as prevailing winds and high tides. It is the first large-scale sighting of the species in Korea in two to three years.

Unlike most jellyfish, which are made mostly of water and disappear quickly after death, the jellyfish has a chitinous exoskeleton that remains intact, leaving visible remnants on the beach.

A swarm of jellyfish appears on a beach in Jeju. The bright blue, mold-like creatures are identified as "Porpita umbrella." [SCREEN CAPTURE]

Last Tuesday and Wednesday, swarms of the species appeared along Sagye Beach and Pyoseon Beach in Seogwipo, prompting authorities to temporarily restrict beach access.

News of the sightings has raised concerns among tourists planning trips to Jeju, particularly about entering the water. Fortunately, the species is known to have only mild venom.

Experts recommend rinsing the affected area with seawater or saline solution in the event of a sting and avoiding the use of tap water or alcohol. Beachgoers are also advised to wear shoes to avoid stepping on jellyfish washed ashore.

The National Institute of Fisheries Science has asked the public to avoid approaching the jellyfish and to promptly report any sightings.

BY JEONG JAE-HONG [[email protected]]