Authorities in Melbourne are urging swimmers to stay out of the water after thousands of lion’s mane jellyfish washed ashore across Port Phillip Bay.
The jellyfish have stretched along large sections of the coastline, prompting warnings from local councils and lifesaving groups as the marine animals clustered in shallow water and on beaches.
A January 27 report from The Guardian said sightings had been recorded from Altona to Blairgowrie on the Mornington Peninsula, with some locals referring to the surge as “jellygeddon.”
Neil Blake, the bay’s keeper, told the outlet the scale of the event was unusual, noting that a bloom of similar size had last been recorded about four years ago.
Authorities warn swimmers to avoid the water
Blake said the influx followed an earlier bloom of bluebottle jellyfish that washed up on Victorian beaches in December, adding that numbers have fluctuated with changing weather patterns.
“Their presence ebbed and flowed with the wind and waves,” he said, noting that the amount of jellyfish had declined over the past week. One Melbourne beach was temporarily closed after what he described as a “massive smack” of jellyfish arrived.
Most of the jellyfish washing ashore were roughly the size of a peach, Blake added, though they carried long tentacles capable of stinging and stretching more than a meter.
Bayside City Council, which oversees beaches from Brighton to Beaumaris, addressed the situation on social media, calling it “the joys of an Australian summer.” In a Jan. 19 Facebook post, the council described the sightings as “a natural and fairly common seasonal occurrence,” while advising visitors to take care when swimming, walking barefoot, or bringing dogs to the beach.
Life Saving Victoria also issued guidance, warning people to avoid entering the water when jellyfish are visible.
“If you can see jellyfish in the shallows, don’t swim,” a spokesperson said. “Stick to patrolled beaches and always swim between the red and yellow flags.” The group also cautioned against touching jellyfish on the sand, noting they “can still sting.”
“If you’re stung, get out of the water and seek help from a lifesaver or lifeguard if present,” the spokesperson added. “Rinse with seawater, remove any tentacles carefully, and use hot water for pain relief.”
Marine expert Jonathan Lawley said lion’s mane jellyfish are poor swimmers that tend to drift with wind and currents.
“We often only observe them when the tide and currents bring them to shore; that’s when we see these huge numbers,” he said.
This isn’t the first time a mass number of jellyfish caused issues, either. Back in August 2025, a swarm shut down four nuclear reactors in France after clogging the facilities’ cooling water filters.
