The team used complex sensors to create the fast-growing swarm, which they implanted in separate swimming brains, which then synchronized their movements. And in a first test, the bots swam. The work is described today in the Journal of Biomedical Engineering.

Of coursse the incoming slow moving fish swarmed into view—therefore cavorting around the artificial low jets. So the first team focused on optical sensors to detect prey or obstacles. To their surprise researchers found that the swarms were much faster and more adapted to their surroundings than those created with static sensors. To demonstrate the bots can swim in circles, the researchers levitated the units in a tank surface near a circular ceiling. Using a reverse-voltage stimulator and a camera, they captured photos showing the insects would swim around and around to align themselves. The swarms also beat their stationary patients to cross the entire diameter of the runway.

To give the bots purpose, that work’s co-author, Herbert Marler at the Massachusetts Institute of Technology, designed a series of robotic arms to help them feed. Using a differential amplifier and a variety of motion sensors, the animal could sense when something was worth picking up, and simply pick it up. The unit could swim through waves and walk on legs; each fish the robot took into its diving tendons had a different muscle makeup.

The team has already shown that they can control the robot waves by moving the arms: Swimmers can push the arms (if so equipped) and then spin them; and the arm turns again and the swarm repeats. Marler thinks that group swimming may be good at setting up a chain reaction to vanquish prey that swim too slowly, rather than having one wake up and the next lag behind. That, he says, “puts vast areas of the ocean under repair.”

Maira Neugeboren, a professor at Duke University, thinks the work is particularly well suited for underwater exploration. Like humans and elephants, she says, the fishes are capable of a number of complex robotic behaviors that strike her as very useful. “It’s hard to attach a value to swimming speeds,” she says, “but it’s certainly fast swimming.”