Physalia megalista, 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 mu