What mysterious, gelatinous, clear blob that you might find washed up on a beach looks like a jellyfish but isn’t? Meet the sea salp. It typically lives in deep waters, where its barrel-shaped body glides around the ocean by jet propulsion, sucking in water from a siphon on one end and spitting it back though another. It swims alone for part of its life. But it spends the rest of it with other salps, linked together in chains arranged as wheels, lines or other architectural designs.

“They’re totally cool, and totally beautiful to watch underwater,” said Kelly Sutherland, a marine biologist at the University of Oregon.

Over years of watching them swim in chains, she made a surprising discovery. They synchronize their strokes when threatened by predators or strong waves and currents. But while linked together in day-to-day life, each salp in the chain swims at its own asynchronous and uncoordinated pace. Counterintuitively, this helps salps that form linear chains make long nightly journeys more efficiently. She and a colleague, Daniel Weihs, an aerospace engineer at the Israel Institute of Technology, presented their findings on Wednesday in Journal of the Royal Society Interface.

The life story of the sea salp is peculiar. Each one starts life as a female, then switches to male and never switches back, but no one knows why.