Stock Photo - Portuguese man o' war, Physalia physalis, washed ashore. Despite its appearance, the Portuguese man o' war is not a true jellyfish but a siphonophore, which is not actually a single multicellular organism (true jellyfish are single organisms), but a colonial organism made up of many specialized animals of the same species, called zooids or polyps. These polyps are attached to one another and physiologically integrated, to the extent that they cannot survive independently, creating a symbiotic relationship, requiring each polyp to work together and function like an individual animal. The stinging, venom-filled nematocysts in the tentacles of the Portuguese man o' war can paralyze small fish and other prey. Detached tentacles and dead specimens (including those that wash up on shore) can sting just as painfully as the live organism in the water and may remain potent for hours or even days after the death of the organism 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 1 to 3 hours. However, the venom can travel to the lymph nodes and may cause symptoms that mimic an allergic reaction including swelling of the larynx, airway blockage, cardiac distress, and an inability to breathe. One of the problems with identifying these stings is that the detached tentacles may drift for days in the water, and the swimmer may not have any idea if they have been stung by a man o' war or by some other less venomous creature. Strong winds may drive them into bays or onto beaches. They can sting while beached; the discovery of a man o' war washed up on a beach may lead to the closure of the beach. Portuguese men o' war have no means of propulsion, and move driven by the winds, currents, and tides. Azores 2019