Physalia pelagica; Print; The Portuguese man o' war (Physalia physalis); also known as the man-of-war; is a marine hydrozoan found in the Atlantic; Indian and Pacific Oceans. It is one of two species in the genus Physalia; along with the Pacific man o' war (or Australian blue bottle); Physalia utriculus. Physalia is the only genus in the family Physaliidae. Its long tentacles deliver a painful sting; which is venomous and powerful enough to kill fish and even humans. 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.