People are being warned to stay out of the sea along parts of Dublin's coast line.
It follows sightings of a number of Lions Mane, one of the most dangerous breeds of jellyfish.
The Lions Mane has hundreds of tentacles capable of causing severe stings.
Local Fianna Fail Councillor Cormac Devlin says "these particular ones, given the size of their tentacles, while they appear to be a long distance away, it's the tentacles that can actually cause the severe sting."
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