The Portuguese man o' war (Physalia physalis), also known as the Portuguese man-of-war, Man-Of-War, or bluebottle, though often mistaken as a jellyfish, is a marinecnidarian of the family Physaliidae. Its venomous tentacles can deliver a painful sting.
Despite its outward appearance, the Portuguese man o' war is not a jellyfish but a siphonophore, which differs from jellyfish in that it is not actually a single multicellular organism but a colonial organism made up of many highly specialized minute individuals called zooids.[SUP][1][/SUP] These zooids are attached to one another and physiologically integrated to the extent that they are incapable of independent survival.