Lifeguards across the country are combing beaches for infestations of Lion's Manes and Portugese Man O'War jellyfish.
Up to 17 Lion's Manes jellyfish were found at Sandycove beach in Dublin yesterday, causing the beach to be closed as a precautionary measure and there are also warnings at Seapoint and Killiney beaches.
These particular breeds can cause a severe sting to bathers sending some into an anaphylactic shock.
John Leech from Irish Water Safety says people need to be careful and heed the warnings in place.
He said: "The lifeguards are literally on jellyfish patrol. They are using their boats and surf rescue boards to keep an eye out for the jellyfish.
"Sandycove is closed at the moment, because an infestation of them came in, and they felt it was safer to close it rather than risking the public getting stung by them."