These monsters can cause serious pain, and even death.

Cork County Council Beachguards raised the red flag at Garretstown beach yesterday (Sunday, August 22nd) following the discovery of a Portuguese man o’war jellyfish on the sands.

The deadly jellyfish was the second one to be discovered in Cork over the weekend, with another found on the nearby Owenahincha beach on Saturday. The beachguards of Cork County Council tweeted on Saturday: “Beachguards will be walking their area of operations first thing when they come on duty. To see if any more PMOWs have washed up. If more PMOWs are found, red flags will be flown.”

Checks on beaches in the area will continue this morning, with red flags set to be raised unless no Portuguese man o’wars are found.

According to National Geographic, the creatures are covered in venom-filled nematocysts used to paralyze and kill fish and other small creatures. For humans, a man-of-war sting is excruciatingly painful, and can be deadly — though this is rare. Worryingly, the little monsters can still pack a very serious sting even when washed up on the beach — so great care must be taken in any area where they have been spotted.

Beachguards Cork County Council confirmed that a third such jellyfish had been found at Garrylucas later on Sunday.

Interesting, the Portuguese man o’war is not actually, technically a jellyfish, but a siphonophore, an animal made up of a colony of organisms working together.

Header image via Twitter/@CorkCoCoBeachLG