Killer ‘jellyfish’ Portuguese man o’war which can grow to 160ft long are washing up on Britain’s beaches

The creatures can seriously harm a person with just one sting, even if they are already dead

Portuguese man o’war, creatures often mistaken for jellyfish, have washed up on the shores in parts of Britain.

Wildlife experts have warned people to steer clear from these creatures as they are potentially fatal for humans.

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At a glance: 5 Key Points

  • Nicknamed as “Floating Terror”, these creatures have been spotted near tourist areas in Cornwall, Sennen Beach and Porteras Cove.
  • They are often mistaken for jellyfish, can stretch their tentacles up to an incredible 160ft long and can kill a human even if the creature is dead. 
  • Fatal incidents are rare, but stormy weather has driven these creatures up from their usual open seas territory to the shallow waters of Britain’s coastline.
  • They are known to wash up on British shores between September and December.  
  • People are urged not to approach these creatures and to divert any pets from any found on beaches. 

What’s been said

A Wildlife Trust spokesman said: “First of all, the Portuguese man o’war is not a jellyfish. It is a colonial hydrozoan, made up of small individual animals called zooids - each with their own specific function, e.g. feeding or breeding.

“They can’t live separately and function together as one ‘animal’.

“The Portuguese man o’war lives at the surface of the open ocean, held afloat by a gas-filled bladder. This has a crest-like structure at the top which acts as a sail.

“They can’t swim and are at the mercy of the winds — which is why they often end up washed ashore after big storms.

“They are fearsome predators, catching small fish and crustaceans with their long stinging tentacles.

“It’s these tentacles that you need to watch out for too — they can sting long after the animal has died.”


Portuguese man o’war can be found in the open water, sometimes in groups up to 1000, but due to their inability to propel themselves, they move with strong currents and the wind.

They can wash up on British beaches from September to December, but can still harm people and pets long after the creature is dead.

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