The Portuguese Man O’ War, known scientifically as Physalia physalis, is often mistaken for a jellyfish, when in reality it is a siphonophore, a colonial organism made up of multiple smaller zooids. The Portuguese Man O’ War is considered to be the same species as the Pacific Man O’ War. The Portuguese Man O’ War consists of its top, called a pneumatophore, which is mainly translucent blue with hints of purple, that is filled with carbon monoxide and acts as a sail and flotation device for the organism. Dangling from its top are the Portuguese Man O’War’s killer tentacle zooids which kill fish, and have even killed humans, as it floats along the top of the ocean surface. The Portuguese Man O’ War lives solely on the ocean’s surface making it a member of the neuston, a highly complex ecology of ocean surface dwelling creatures, of which little is known.