The Portuguese Man O’ War is an object of beauty – and at the same time, dread. These strange, floating creatures are dangerous to humans, causing very painful stings. They can be such a nuisance that warning signs are often erected on beaches when the Man O’ War are particularly prevalent.

These jellyfish have no means of propulsion and are ruled entirely by currents and tides. The large purple-blue balloon is filled with carbon monoxide, nitrogen, oxygen and argon, so it floats above the water surface with long tentacles dangling below. You can find them in open water, shallow water, and stranded on beaches. Even detached portions of tentacles can sting, so never touch one that has washed ashore.

The Man O’ War is interesting in that it is actually a colony of animals working together. Each smaller animal has its own special task. For instance, one animal is the balloon, while other members of the colony are found in the long tentacles. These tentacles can stretch for tens of feet, some even reaching 150 feet long, and are used to immobilize and kill prey. Because these tentacles can reach such lengths, it’s important to exit the water as soon as you see that floating balloon on the surface.

So how did this creature get its unique name? It comes from the 18 th century artillery ship, which the animal resembles in full sail!