A stark warning has been issued over a swarm of potentially deadly jellyfish that are washing up along Louth's shoreline.
Hundreds of Lions Mane jellyfish have come ashore at Annagassan, Port and Clogherhead beaches over the last week.
The brainless stingers could be potentially deadly as their stings can cause swimmers to go into anaphalactic shock.
Irish Water Safety said this week: “The Lions mane Jellyfish has been reported to us on the following beaches Portmarnock, Malahide, Sutton and Bettystown.
“Lifeguards ensure your safety on our beaches and will be patrolling on their surf rescue boards to ensure that they do not pose a threat to members of the public.
“The CEO is also alerting the public that due to the current spell of good weather when more people will be enjoying our waters, these potentially dangerous jellyfish are likely to appear on more of our beaches in the coming weeks.
“The sting from these jellyfish can cause anaphylactic shock and we have had a number of people hospitalised as a result of a sting from these venomous Jellyfish.
“The sting from their tentacles lasts many days after they have died.
“Members of the public should report the sightings of these two jellyfish to the relevant local Authority Water Safety Development Officer.”
The Lion's Mane jellyfish (Cyanea capillata) is also known as the giant jellyfish or the hair jelly, and is the largest known species of jellyfish on the planet.
It can grow to length of up to 37 metres and while not nearly as deadly as other species of tropical jellyfish, it can give swimmers a painful and potentially fatal sting, given that some people suffer an allergic reaction to them.
Most encounters however just cause temporary pain and localised redness of the skin.
On July 21, 2010, around 150 people are thought to have been stung by the remains of a lion's mane jellyfish that had broken up into countless pieces in Rye, New Hampshire, in the United States.
Some people believe that given the size of the species, the incident could have been caused by just one jellyfish.