Head to head
By-the-Wind Sailor vs Portuguese Man o' War
A by-the-wind sailor and a Portuguese man o' war are both colonies of specialised individuals drifting the ocean surface propelled by a sail rather than active swimming, but one is considerably more dangerous to encounter than the other.
| By-the-Wind Sailor | Portuguese Man o' War | |
|---|---|---|
| Sail type | Small, rigid, fixed diagonal angle | Large, flexible, inflatable float |
| Sting severity | Too weak to usually feel | Painful, occasionally serious |
| Tentacle length | Short | Long, up to many metres |
| Organism type | Colonial hydrozoan | Colonial hydrozoan (siphonophore) |
| Movement | Passive, wind-driven | Passive, wind-driven |
| Typical size | A few centimetres | Float up to around 30 centimetres |
| Mass beaching events | Common | Common |
| Conservation status | Least Concern | Least Concern |
By-the-Wind Sailor vs Portuguese Man o’ War: common questions
Is it safe to touch a by-the-wind sailor but not a Portuguese man o’ war?
A by-the-wind sailor's stinging cells are generally too weak to be felt through human skin, making it considerably safer to encounter than a Portuguese man o' war, whose much longer tentacles carry a sting capable of causing real pain and, in some cases, more serious reactions, so caution is still warranted around any washed-up colonial hydrozoan even when one species is typically harmless.
Why do both animals wash up on beaches in large numbers at the same time?
Both the by-the-wind sailor and the Portuguese man o' war move passively at the mercy of wind and current rather than swimming actively, so sustained onshore winds can push large numbers of either species toward shore simultaneously, producing the dramatic mass beaching events periodically reported along affected coastlines.
Are these two animals closely related?
Yes, both the by-the-wind sailor and the Portuguese man o' war are colonial hydrozoans, placing them in the same broad group of stinging marine organisms, though the Portuguese man o' war is specifically classified as a siphonophore with a more complex colony structure and considerably more potent stinging tentacles than its smaller relative.