The Irish Water Safety has issued a warning over sightings of Portuguese Man-of-Wars on Irish shores.
Sightings have been noted in Kerry, in Waterford on beaches in Tramore, Ardmore and in Cork on Inchydoney and Schull.
The organisation says that with a promising weather forecast for the weekend, swimmers, surfers and families enjoying the beach are at a high risk of encountering them.
Other aquatic users will be at a lesser risk and there is a risk that they may drift further north depending on wind direction.
Man-of-wars are found, sometimes in groups of 1,000 or more, floating in warm waters throughout the world's oceans.
The stinging, venom-filled nematocysts in the tentacles of the Portuguese man-o-war can paralyse small fish and other prey.
Detached tentacles and dead specimens (including those that washed up on shore) can sting just as painfully as the live creature in the water.
The stings may remain potent for hours or even days after the death of the creature or the detachment of the tentacle.
Stings usually cause severe pain to humans, leaving whip-like, red welts on the skin that normally last two or three days after the initial sting, though the pain should subside after about an hour.
However, the venom can travel to the lymph nodes and may cause a more intense pain.
There can also be serious effects, including fever, shock, and interference with heart and lung function.
Stings may also cause death, although this is extremely rare.
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