The Portuguese Man O’War (Physalia physalis) is absolutely alien-looking. With its bulbous top, dangling tentacles and iridescent coloring, this unusual invertebrate will make anyone do a double-take. But what is it, exactly? Read on for five facts about the Portuguese Man O’War.

It looks like a jellyfish, but it’s not a jellyfish.

Portuguese Man O’Wars may resemble jellyfish because of their “bell” and tentacles, but they’re actually completely different. Man O’Wars are siphonophores, which are a type of hydrozoan comprised of many animals living together in a colony. Although both jellyfish and the Man O’War are part of the phylum Cnidaria, true jellyfish are in the class Scyphozoa, while Man O’Wars are in class Hydrozoa.

They rely on team work.

Each Portuguese Man O’War is comprised of genetically-identical individuals called zooids. Just like a coral head looks like one animal but is made up of many polyps, a Portuguese Man O’War looks like one organism but is made of many zooids. Zooids can perform different tasks depending on the needs of the organism. Parts of the animals include the pneumatophore, which is filled with gas and floats on the ocean surface; the gonozooids and gastrozooids, which are used for reproduction and digestion; and the dactylozooids, which are used for hunting and capturing prey.

Their tentacles can be very, very long.

Portuguese Man O’War tentacles can stretch 165 feet below the surface—that is almost as long as the Leaning Tower of Pisa is tall! Not all Man of War’s have such impressive appendages, though. The average tentacle length is about 30 feet.

They get their name from historical ships.

The Portuguese Man O’War’s inflated pneumatophore resembles the sail of a 18th-century Portuguese warship, which is where it got its unique name! The pneumatophore is typically a distinctive blue or purple color and can float half a foot above the ocean surface.

Getting stung by a Portuguese Man O’War is not a good time.

Portuguese Man O’Wars have a nematocysts, or stinging cells, in their tentacles, which they use to stun and capture their prey. Unfortunately, they can also sting humans, even if the animal is dead or the tentacles are no longer attached. The venom is very painful to humans, and can result in skin welts or even an allergy-like response. If you see a Portuguese Man O’War, admire from afar and do NOT touch! If you are stung, pay close attention to your symptoms and seek medical attention if needed.