Portuguese Man o' War

The Portuguese Man o' War is not a jellyfish but a colonial hydrozoan—a floating superorganism of specialized polyps working in concert. A gas-filled bladder, often bright blue or purple, keeps the colony at the surface, with tentacles dangling up to 30 m below. Divers encounter it in warm and temperate oceans, drifting with currents; it does not swim. The nematocysts (stinging cells) on its tentacles are potent and can cause painful welts even after the animal has washed ashore.