Physalia physalis develops from a single larva that buds zooids, each differentiating for one job. The pneumatophore is the gas-filled float. Dactylozooids are the long tentacles that catch prey. Gastrozooids digest it. Gonozooids handle reproduction. The zooids are attached and physiologically integrated, so none functions alone, and the whole assembly is the organism in any practical sense.
That structure puts it in Hydrozoa alongside hydroids, not in Scyphozoa with true jellyfish. The visible float is filled with gas including carbon monoxide, and the animal can deflate it briefly to duck beneath the surface.
Steering is entirely passive. The crest sits at an angle and acts as a sail, and populations include left-sailing and right-sailing forms, which spreads the risk that one wind pattern strands them all. Tentacles commonly trail several metres and occasionally far longer. Stings remain active in beached specimens for a considerable time, and vinegar, the standard advice for cubozoan stings in Australia, is not recommended here because evidence on Physalia is conflicting.