A marine colonial organism (siphonophore, family Physaliidae) that drifts on the ocean surface with its pneumatophore (gas-filled bladder, up to 30 cm across) above the surface and its tentacles below. The tentacles bear stinging cells (nematocysts) that can deliver a painful sting to humans and that paralyze the small animals on which it feeds. There are two species, the Atlantic (Physalia physalis) and the Indo-Pacific (P. utriculus) Portuguese man-of-war, which is smaller.