Recently, a robotic impostor swam through the crystal blue waters off Fiji, blending in with the fish teeming around the coral reefs. Unlike the Cylons in Battlestar Galactica, however, this infiltrator was on a peaceful mission.

In a new study published in Science Robotics, researchers at MIT unveil what they say is the most advanced robotic fish of its kind ever built. Armed with a camera and a lifelike wiggle, the device could one day help biologists monitor the health of marine habitats without stressing out their aquatic denizens.

The Soft Robotic Fish, SoFi for short, is 18.5 inches long from snout to tail and weighs about 3.5 pounds. It can dive 60 feet underwater and is powered by enough juice for about 40 minutes of exploration.

Why they did it

As climate change and overfishing wreak havoc on oceans, scientists are racing to study marine life in detail. But scuba-diving humans don't exactly blend in, which can make it hard to watch some animals up-close. SoFi could act as marine biologists' unobtrusive eyes and ears.

“When we were designing the robot, we tried to make sure that it's moving to conserve the life we're trying to observe,” says co-author Joseph DelPreto.

How they did it

To build better aquatic robots, researchers have mimicked tuna, jellyfish, and lobsters, and they've also built robots out of pliable materials, such as the squishy “octobot.”

“There will be a revolution in some fields with soft robots,” says SoFi's co-creator Robert Katzschmann, a Ph.D. candidate at MIT's Computer Science & Artificial Intelligence Lab. “It may be for underwater locomotion, but also walking robots or grasping robots. This whole field will see changes.”

Since 2014, MIT roboticist Daniela Rus and her students, including Katzschmann and DelPreto, have built various prototypes of robotic fish. But these early versions of SoFi couldn't be controlled remotely, nor could they withstand dives more than three feet underwater.

Now, Katzschmann and his colleagues have ruggedized SoFi and reinvented its buoyancy control system. They also gave SoFi a remote control, letting a scuba diver drive it from up to 50 feet away. To work in water, the system uses pulses of ultrasound to communicate. It's controlled by a waterproofed retro gamepad that DelPreto designed.

What they found

So far, SoFi's disguise might be working. During the recent test dives around Fiji, reef fish swam within inches of SoFi without being obviously spooked. For now, the robot interloper recorded only video, but its creators envision adding other sensors, such as thermometers.

Future versions of SoFi will also improve the fish's swimming and vision, and its creators say they're sketching out plans for SoFi “swarms”: schools of artificial fish set loose to monitor ocean health, perhaps recharged by solar-cell platforms floating on the water's surface.