Portuguese Man o' War
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40 free Portuguese Man O' War trivia questions with answers — trivia quiz, new questions added Oct 2026.
The Portuguese man o' war looks like a jellyfish, drifts like a toy boat and carries venom that sends beachgoers running for the dunes. Almost everything about it is stranger than it first appears, from what the animal actually is to the gas that keeps it afloat. This quiz gathers the best fun facts about the Portuguese man of war: how it got its name, how it travels with no way to steer, which creatures eat it or hide among its tentacles, and what to do after an encounter with one. It is written for curious beachgoers, students and anyone who has spotted a strange balloon on the tideline and wondered what it was. Every answer comes with a short explanation.
30 of 40 questions with answers and explanations. Play the quiz
Q 01Often mistaken for a jellyfish, the Portuguese man o' war belongs to which group of sea animals?
Siphonophores
Siphonophores are colonies of specialised, genetically identical units working together as one body, while a true jellyfish is a single animal. The two groups are close relatives.
Q 02Which animal, immune to the venom, rips tentacles off the Portuguese man o' war to wield as weapons?
Blanket octopus
Blanket octopus males and young females tear the tentacles off and carry them for attack and defence. A threatened female can also unfurl net-like membranes to look far bigger.
Q 03Why might a beach be closed when a dead Portuguese man o' war washes up on the sand?
It can still sting
It can still sting for hours or even days after death, and so can a tentacle that has broken away. Beached specimens hurt just as much as live ones in the sea.
Q 04The Portuguese man o' war takes its name from its float's likeness to which object?
A warship under sail
A warship under sail is what the gas-filled float was thought to look like, specifically an 18th-century Portuguese vessel. 'Man-of-war' was old naval jargon for a powerful armed ship.
Q 05Which sea slug eats Portuguese man o' war and keeps the stolen stinging cells for its own defence?
Blue dragon
Blue dragon is a common name for Glaucus atlanticus, a slug about an inch long that packs the stolen cells into its finger-like cerata. Its own sting can outdo that of the animal it ate.
Q 06The float of a Portuguese man o' war holds mostly air plus which poisonous gas the animal makes itself?
Carbon monoxide
Carbon monoxide comes from the animal's own gas gland and can make up as much as 13% of what is inside the float. The rest is ordinary air that diffuses in from outside.
Q 07Typically about 10 metres long, Portuguese man o' war tentacles can reach roughly what length?
100 feet
100 feet, or about 30 metres, is the reach of the longest tentacles. Muscles inside them contract to haul a paralysed catch up to the colony's many mouths.
Q 08Which reptile, shielded by thick skin in its throat, regularly eats the Portuguese man o' war?
Loggerhead sea turtle
Loggerhead sea turtle skin, including that of the tongue and throat, is too thick for the stings to get through. Very few other predators will touch the animal.
Q 09A Portuguese man o' war's polyps hunt and feed in close coordination despite lacking which of these?
A brain
A brain is missing from the whole colony, yet its specialised polyps share out the work of floating, catching prey, feeding and reproducing as if they were one animal.
Q 10Which nickname, inspired by the colour of its float, is the Portuguese man o' war also known by?
Bluebottle
Bluebottle comes from the purple-blue colour of the gas-filled float, which can stand several inches above the waterline like a tiny balloon.
Q 11In which country do Portuguese man o' war sting an estimated 10,000 beachgoers every summer?
Australia
Australia logs most of them on its east coast, where strong onshore winds push whole fleets onto exposed surf beaches.
Q 12After the tentacles are removed, a Portuguese man o' war sting is eased by a 20-minute soak in what?
Hot water
Hot water at about 45 °C (113 °F) is the standard soak, and the heat is thought to break down proteins in the venom.
Q 13Where does the Portuguese man o' war mostly live, drifting at the surface in fleets of 1,000 or more?
Warm tropical seas
Warm tropical seas and their subtropical neighbours are home, though winds and currents can carry whole fleets far beyond them onto cooler coasts.
Q 21What is the scientific term for the gas-filled float that keeps a Portuguese man o' war at the surface?
Pneumatophore
Pneumatophore is the name of the float, which counts as one modified member of the colony and can grow to about a foot in length.
Q 22The genus name Physalia, given to the Portuguese man o' war, comes from a Greek word with which meaning?
Bladder
Bladder is the sense of the Greek root, a nod to the gas-filled float. The species name physalis repeats the same word, so the full scientific name says it twice.
Q 23Which Swedish naturalist first described the Portuguese man o' war, in his book Systema Naturae?
Carl Linnaeus
Q 14What makes up most of the prey a Portuguese man o' war snares in its trailing tentacles?
Small fish
Small fish and fish fry account for roughly 70 to 90 percent of the catch, with shrimp and other plankton-sized animals filling out the menu.
Q 15What mark does a Portuguese man o' war sting typically leave on human skin for two or three days?
Whip-like red welts
Whip-like red welts trace exactly where each tentacle touched the skin. They come from irritating substances in the tentacles, not from any cutting action.
Q 16How can a Portuguese man o' war briefly escape a threat at the sea surface?
It deflates and sinks
It deflates and sinks only briefly, letting gas out of the float that normally keeps it riding high on the waves.
Q 17The Portuguese man o' war shares the phylum Cnidaria with which other sea creatures?
Corals and sea anemones
Corals and sea anemones are fellow cnidarians, a group defined by its stinging cells. Jellyfish belong to it too, which is why the man o' war looks so familiar.
Q 18The violet sea snail hunts Portuguese man o' war at the surface while hanging beneath what?
A raft of bubbles
A raft of bubbles, made by trapping air in its own mucus, keeps the snail and its paper-thin shell at the surface, where its stinging prey drifts.
Q 19A Portuguese man o' war's feeding polyps spread their mouths over a catch and break it down with what?
Digestive enzymes
Digestive enzymes that dissolve proteins, carbohydrates and fats do the work. Each tiny mouth can stretch from a millimetre or two to more than 20 mm across.
Q 20What are the genetically identical units that make up a Portuguese man o' war colony called?
Zooids
Zooids come in several body types, each built for one job such as stinging, feeding or breeding. None could survive apart from the rest of the colony.
Carl Linnaeus named it in 1758, the first animal of its group known to science. He filed it in a genus that today holds very different creatures.
Q 24The Portuguese man o' war was first placed in the genus Holothuria, which now contains which animals?
Sea cucumbers
Sea cucumbers are soft-bodied, limbless animals of the ocean floor, nothing like a surface drifter. The man o' war was moved to a genus of its own in 1801.
Q 25What are the microscopic venom capsules that line a Portuguese man o' war's tentacles called?
Nematocysts
Nematocysts each hold a coiled, barbed tube that shoots outward on contact and injects venom into whatever touched it.
Q 26The man-of-war fish lives among Portuguese man o' war tentacles, avoiding stings mainly through what?
Agile swimming
Agile swimming, aided by an unusually high count of 41 vertebrae, lets it weave between the large tentacles. It also nibbles the smaller ones for food.
Q 27Which giant fish, once thought to live mainly on jellyfish, also eats the Portuguese man o' war?
Ocean sunfish
Ocean sunfish, among the largest ray-finned fish in the world, turned out to have a far more varied diet than their jelly-eating reputation suggested.
Q 28Portuguese man o' war floats lean either left or right, so the same wind does what to a drifting fleet?
Splits it two ways
Splits it two ways: left-leaning sails veer right of the wind and right-leaning ones veer left, so no single gust can strand a whole population on shore.
Q 29Every polyp in a Portuguese man o' war colony is genetically identical because all grow from what?
A single fertilized egg
A single fertilized egg gives rise to the whole colony, so its members are clones that stay physically connected and work much as organs do in one body.
Q 30How does a growing Portuguese man o' war colony add new polyps to its body?
Budding
Budding lets the young colony clone fresh members as it grows. Tentacles, mouths and reproductive parts are all added this way, one new unit at a time.