The Atlantic Portuguese man o' war (Physalia physalis), also known as the Man-of-war, bluebottle, or floating terror, is a marine cnidarian of the family Physaliidae. Its venomous tentacles can deliver a painful sting. In spite of its outward appearance, the Portuguese man o' war is not a common jellyfish but a siphonophore, which is distinguished from jellyfish in that it is not a a single multicellular organism, but a colony of specialized minute individual organisms called zooids. These zooids are attached to one another and physiologically integrated to the extent that they are incapable of independent survival and take on the function of a single organism.