Fears have been raised that Portuguese man-of-war could be heading to Devon's shores.
Marine experts have said weather conditions are ideal for an invasion of the creatures which normally live far away from UK seas.
They add that this summer's weather patterns match the last time they were spotted in British waters five years ago.
And The Daily Mail report a strong south-west wind caused by Hurricane Bertha could send the creatures towards Britain.
This coupled with more plankton in the shallow waters off the coast thanks to the hot summer, means conditions are perfect for their arrival.
The news comes as the Southwest coast has been identified as a hotspot for jellyfish sightings in a new report which analysed where and when the creatures appear.
The University of Exeter study – published in the Journal of the Marine Biological Association – was based on more than 5,000 jellyfish sightings, of eight different species, sent to the Marine Conservation Society (MCS) between 2003 and 2011.
The Portuguese man-of-war drifts virtually invisible just below the surface and have tentacles which can wave in the current up to 160 feet from its body.
The name "man o' war" comes from the man-of-war, an 18th-century armed sailing ship, and the cnidarian's supposed resemblance to the Portuguese version at full sail.
If stung usually the victim suffers agonisingly painful, large red rashes which can turn into weals and take months to heal.
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Doctors say bathers and beach-goers should seek immediate advice from coastguards or lifeguards if they are stung by any type of jellyfish.
The last time the UK saw an invasion of Portuguese men-of-war on our beaches was in the summer of 2009 when at least eight of them floated on to Tregantle beach in Cornwall.
Another two were spotted in estuaries between Bantham and Bigbury in Devon.
A spokesman for the National Marine Aquarium said the sail-like creatures are blown here by fair winds and favourable currents in hot summers to feast on vast 'soups' of plankton which appear in shallow water close to holiday beaches.
A spokeswoman for Brixham coastguard said 'There have been a number of reports of jellyfish off the coast this year.
'Normally it depends on the age of the person who has been stung whether or not they require medical attention.
'If it's a child or someone over 60, which may be the case here, then it is best if they are checked over by paramedics.'
'It's really exciting - the last time we had large numbers of them was 12 years ago. There's been lots of reports coming in from the public.
'The hotspots seem to be the south coast including Falmouth and Fowey and almost up to Devon. They are amazing creatures.'
