Portuguese Man o War

The Portuguese man o' war, also called the man-of-war or bluebottle, is a marine hydrozoan found in the Atlantic, Indian and Pacific oceans that superficially resembles a jellyfish but is in fact a siphonophore, a colonial organism made up of many smaller, genetically identical units called zooids that specialize in functions such as hunting, digestion and reproduction. A gas-filled bladder called the pneumatophore keeps it afloat at the surface while its tentacles, which can reach up to 30 metres long, hang below carrying venomous cnidocytes capable of delivering a sting strong enough to kill fish, crustaceans and, in some cases, humans. A sail atop the pneumatophore, left or right-handed depending on which way it catches the wind, propels the animal across the sea, sometimes in groups as large as a thousand individuals.