A venomous jellyfish known as the 'floating terror' has washed ashore on a beach in Cornwall.

The Portuguese man o'war, which can deliver an agonising sting from long tentacles that trail in the water, may have been blown ashore by winds from the Atlantic Ocean.

The creatures, which are actually siphonophores, colonies of minute organisms that rely upon each other for survival, are normally found in the surface waters of the open ocean.

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Marine experts have warned members of the public not to touch the Portuguese man o' war should they find them on beaches this summer. The creature above was found on the beach at Portheras Cove in Cornwall

Their stings can be so powerful it can incapacitate swimmers, sending them into shock and sometimes even resulting in death.

THE FLOATING TERROR The Portuguese man o' war is a carnivore. It is not actually a single creature but a siphonophore - colonies of minute organisms that rely upon each other for survival, Using their venomous tentacles they traps and paralyzes their prey. They typically feeds upon small marine organisms, such as fish and plankton. Their tentacles can also glow in the dark, a process called bioluminescence, to lure their prey into the stings. The venom they contain also produces a painful sting to humans, even when dead. Stings leave whip-like, red welts on the skin that normally last two or three days after the initial sting and the pain can last several hours. In some cases the venom can travel to the lymph notes and cause more intense pain. Portuguese man o' war is itself eaten by loggerhead turtles and the blanket octopus. Advertisement

The animal was stranded among seaweed on the beach at Portheras Cove in Cornwall.

The Marine Conservation Society, which conducts a survey of jellyfish around the UK, has warned holidaymakers to report any further siting of Portuguese man o' war to the local authorities.

Writing on their Facebook page, they said: '(It) looks super-sweet but is extremely dangerous to humans due to its powerful sting. If you find these little devils in numbers, the local authorities must be alerted.'

It has also asked for any sightings to be reported to the Marine Conservation Society.

Experts have urged the public not to touch the Portuguese man o' war should they find them.

The creatures are rare in the UK, but it is feared strong winds in the Atlantic Ocean has blown some closer to the coastline.

Marine conservation volunteer Delia Webb, of the Friends of Portheras Cove, discovered the creature there.

She said: 'A Portuguese man o' war can deliver a very serious and painful sting and their tentacles are exceptionally long and often quite invisible, so can become wrapped around people's arms, leaving nasty welts that tale weeks to heal.

'In sensitive people, the venom can travel to the lymph nodes, which is very dangerous and has been known to be deadly.

'What is particularly dangerous about them being washed up on British beaches is that since they are so rare on our coasts people will not recognise them.

'In fact, children may mistake them for colourful plastic bags or balloons and try to pop them which could be very dangerous.'

The last time there were significant numbers of Portuguese man o' war washing up on British beaches was in 2012.

Experts have warned that children can mistake the Portuguese man o' war, named because of its shape, for balloons or plastic bags when they are found on the beach, like the one above found at Portheras Cove

Recent warm weather has meant jellyfish numbers have soared around the coast of the UK.

Dr Peter Richardson, biodiversity and fisheries programme manager at the Marine Conservation Society, said it was likely the Portuguese man o' war were being blown to the UK by south westerly winds blowing across the Atlantic Ocean.

He said: 'It looks like we are on course for a record year in terms of jellyfish sightings as we have already had large numbers of barrel jellyfish around the coast and others are turning up now.

'The last time we had any significant numbers of Portuguese man o' war around Britain was in 2012. This sighting might mean more are on the way now.

'However as these are creatures that live in the open ocean, it is very dependent on what is going on out in the Atlantic.

'There is currently very little monitoring of jellyfish around the UK, which is surprising as they can have quite large economic impacts.'

Mrs Webb added: 'The warm waters has meant there has been a huge rise in the number of jellyfish around the coastline and we have been spotting a lot of moon and barrel jellyfish, some very large.

'Both can sting but are not usually as serious as the sting of the Portuguese man o' war.'