Is a portuguese man of war a jellyfish?

The Atlantic Portuguese man o' war (Physalia physalis), also known as the man-of-war, is a marine hydrozoan of the family Physaliidae found in the Atlantic, Indian and Pacific Oceans. Its venomous long tentacles deliver a painful sting, which is venomous and powerful enough to kill fish or (rarely) humans. read more

The Man o’ War is a species of siphonophore, a group of animals that are closely related to jellyfish. The Portuguese man o’ war is recognized by its balloon-like float, which may be blue, violet, or pink and rises up to six inches above the water line. read more

The polyps can detach from the body of the man o'war and float for several days while remaining venomous. Brushing against one can lead to an agonising and potentially lethal sting. A stranded Portuguese man o' war looks a bit like a deflating purple balloon about the size of a Cornish pasty with blue ribbons attached. read more