Dozens of the jellyfish have been sighted in recent days.
A man stung by a dangerous Lion's Mane jellyfish is warning the effects can be long lasting.
Dozens of the dangerous marine creatures have been washing up along the Dublin coastline, prompting warnings for swimmers and bathers.
A sting from the jellyfish can cause nausea and headaches, while in severe cases urgent medical attention is needed - they can also be harmful to dogs.
Patrick Corkery was swimming the North Channel between Northern Ireland and Scotland in 2014 when he was stung multiple times, including on his face.
He had to undergo double open lung surgery in 2016.
It's like being in a busy bar and every person is a jellyfish and you're trying to avoid them.
''Some will be deeper than you so you wont hit them all, but often it's the ones you can't see that sting you because of the lengths of the tentacles'', he said.
''Do I got stung on the face, on the legs and the arms all day long and I could put up with that.
''But internally you don't know how it's affecting you, and after a couple hours my breathing became very difficult, I couldn't keep my head in the water''.
