This organism is not a jellyfish, despite the superficial similarity. True jellyfish are members of Class Scyphozoa (Phylum Cnidaria), whereas the Portuguese man-of-war is in Class Hydrozoa (Phylum Cnidaria). This organism is a colony of hydrozoans. The body is bluish or purplish or pinkish and consists of a gas-filled float plus many long tentacles. The tentacles have numerous nematocysts (stinging cells), used for paralyzing or killing prey.