Invertebrates
By-the-Wind Sailor
Velella velella · also called Velella
A by-the-wind sailor has no way to steer and no interest in trying. A stiff, translucent sail set at a fixed diagonal angle catches whatever wind is blowing and carries the whole colony wherever that wind happens to go, sometimes for thousands of miles, sometimes straight onto a beach alongside thousands of others just like it.
Overview
The by-the-wind sailor, Velella velella, is a colonial marine organism found drifting across warm and temperate ocean surfaces worldwide. A rigid sail propels it passively with the wind, while short tentacles beneath its flat, oval float capture small planktonic prey.
A gentler relative of the man o’ war
Related to the considerably more painful Portuguese man o’ war, the by-the-wind sailor carries a sting too weak for most people to even feel, making its periodic mass beachings a striking but largely harmless sight rather than the hazard its more famous relative represents.
Status
Least Concern — abundant and widespread across warm and temperate oceans, with numbers and distribution shifting naturally alongside wind and current patterns.
By-the-Wind Sailor: common questions
Is a by-the-wind sailor a jellyfish?
Not exactly, though it is related to jellyfish within the same broad group of stinging marine animals called cnidarians, a by-the-wind sailor is specifically a colonial organism made up of many specialised individuals working together, more closely related to the similarly colonial Portuguese man o' war than to a true, single-bodied jellyfish.
Is it safe to touch a by-the-wind sailor washed up on the beach?
A by-the-wind sailor's stinging cells are generally too weak to be felt through human skin, making it considerably less hazardous than its relative the Portuguese man o' war, though it is still generally best practice to avoid unnecessarily handling any stranded stinging marine organism, particularly touching your eyes or face afterward without washing your hands first.
Why do by-the-wind sailors sometimes wash up on beaches by the thousands?
A by-the-wind sailor cannot actively swim against the wind and instead drifts passively wherever its rigid, fixed-angle sail carries it, so sustained onshore winds pushing large numbers of colonies steadily toward shore can result in dramatic mass beaching events, stranding thousands of colonies along a coastline at once.
What eats a by-the-wind sailor?
The blue dragon sea slug is among the best-known predators of the by-the-wind sailor, immune to its mild stinging cells and capable of consuming the colony's tissue while repurposing its unfired stinging cells for its own defense, alongside various fish and other marine predators that also feed on stranded or drifting colonies.