Just about 20% of the total ocean has been explored, with large portions (especially in the deep sea) entirely unmapped. What if the key to exploring them isn’t a billion-dollar submarine, but a drifting jellyfish fitted with a microchip?

Nicole Xu, a mechanical engineer at the University of Colorado Boulder, has spent years analyzing the translucent moon jellyfish. These gelatinous, brainless, creatures are older than dinosaurs, and for an engineer, they’re fascinating.

Contrary to popular belief, jellyfish don’t drift aimlessly. They’re weak swimmers, but they are capable of detecting and swimming against currents. In fact, moon jellies are among the most efficient swimmers on Earth. For every calorie they burn, they can travel farther through water than nearly any other animal. Xu spent years trying to recreate their movements; then, she realized that instead of building expensive machines that mimic jellyfish, she could simply work with the originals.

How to make a cyborg jellyfish

Xu attached tiny pacemaker-like devices that stimulate the jellyfish muscles. She can then control these devices, nudging them left, right, up, or down. With added sensors, these “cyborg jellyfish” could slip into places even the most advanced robots struggle to reach, like the crushing darkness of the deep sea.

“Think of our device like a pacemaker on the heart,” Xu said. “We’re stimulating the swim muscle by causing contractions and turning the animals towards a certain direction.”

In lab tests and early field trials, Xu and her team have successfully steered jellyfish through shallow waters off Massachusetts. Now, in a new study in Physical Review Fluids, they’ve presented another breakthrough: using biodegradable starch particles instead of toxic synthetic tracers to visualize how jellyfish propel themselves through water. That means scientists can study the animals without leaving harmful residues in the ocean.

But this isn’t the only research team approaching this idea.

Half a world away, researchers in Japan are pushing the idea further. In a recent Nature Communications paper, scientists described harnessing the jellyfish’s “embodied intelligence” — the built-in efficiency shaped by half a billion years of evolution. By combining tiny electrodes with machine learning models, they predicted and guided jellyfish movements with surprising accuracy. It suggests a future where biohybrid jellyfish might navigate autonomously, blending natural instinct with digital control.

Why This Matters

The idea is to attach tiny sensor packages to the jellyfish’s bell (the umbrella-shaped body). These would be lightweight, waterproof devices that could measure things like pH, salinity, temperature, and more. The jellyfish would essentially act like roaming weather stations underwater.

Normally, jellyfish don’t bother too much with swimming and will flow with the currents. But if you can “steer” jellies toward areas of interest, that makes the data they acquire all the more important.

This is important both because we don’t know much about the ocean, and because climate change is kicking in.

The ocean is changing fast. As it warms and turns more acidic, ecosystems are shifting in ways scientists can barely track. Traditional research tools like robotic submarines or deep-sea sensors are expensive and limited. A swarm of living, low-cost jellyfish scouts could collect crucial data on temperature, pH, and oxygen levels in places humans almost never reach.

Xu also believes that jellyfish could inspire the next generation of underwater vehicles, ones that move with the grace and thrift of their biological counterparts. “There’s really something special about the way moon jellies swim,” she said. “We want to unlock that to create more energy-efficient, next-generation underwater vehicles.”

Is This Ethical?

The vision is bold. Having a fleet of glowing jellyfish drifting silently into the abyss, relaying back real-time maps of the ocean’s hidden chemistry, is exciting. This could show us how climate change is reshaping the sea in real time, track pollution spreading through currents, or even guide the design of green technologies inspired by nature’s most efficient swimmers.

But splicing electronics with living animals raises thorny questions.

Do jellyfish feel pain? They lack brains and nociceptors, the receptors that warn mammals of harm, yet they can still respond to stress. Xu’s lab watches for signs like excess mucus production or a halt in reproduction. So far, her jellies seem healthy (tiny polyps are budding in her tanks) but she insists ethics must guide the research.

“It’s our responsibility as researchers to think about these ethical considerations up front,” Xu said. “But as far as we can tell, the jellyfish are doing well. They’re thriving.”

For now, Xu’s jellies pulse gently in their tanks, unaware they may soon become pioneers of an entirely new era of exploration. The oldest drifters in the sea may turn out to be humanity’s newest eyes in the deep.

The study was published in the journal Physical Review Fluids.