When cute-looking jellyfish mushroom into a big problem

Can be as deceptive as dangerous varieties of mushroom

An armada of Portuguese Man of War jellyfish came ashore on West Cork beaches after Hurricane Aidan. The sting from their blue 'tentacles' is excruciating. Dog walkers, keep your pets away! 

On Monday, a friend who had walked a dog on Garretstown Beach, in West Cork, afterwards emailed me with a warning: "Keep your dog away from the small, 'plastic balloons' found on beaches after recent storms. They are Portuguese Man of War, and can be deadly."

Overnight, hundreds of these balloon-like jellyfish had been washed onto the sands and blown by the hurricane above the limits of the highest tides.