Tunicates -- "A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata which is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords." Wikipedia
Portuguese Man O' War (Physalia physalis), is a jellyfish-like marine invertebrate of the family Physaliidae. Its venomous tentacles can deliver a powerful sting. Despite its outward appearance, the Man o' War is not a jellyfish but a siphonophore, which differs from jellyfish in that it is not actually a single creature, but a colonial organism made up of many minute individuals called zooids.
From Wikipedia - The siphonophores, are an order of the Hydrozoa, a class of marine invertebrates belonging to the phylum Cnidaria. Although a siphonophore appears to be a single organism, each specimen is actually a colony composed of many individual animals. Some siphonophores superficially resemble jellyfish, like the dangerous Portuguese Man o' War (Physalia physalis). With a body length of 40–50 m, another species of siphonophore, Praya dubia, is one of the longest animals in the world.