On a misty morning in the San Juan Islands, the water lies flat and silver – a mirror for the low clouds pressing in from the Strait of Juan de Fuca. From the deck of a small research vessel, a team of engineers and oceanographers lowers a coil of slender fibre optic cable into the sea. The line unspools quietly, slipping beneath the surface with barely a ripple.

To most onlookers, it might look like another routine deployment – perhaps a maintenance crew tending to Washington State’s digital lifelines. But for Dr. Shima Abadi and her colleagues at the University of Washington, this cable carries an entirely different kind of potential.

“This isn’t about transmitting data,” Abadi says, watching the cable disappear into the depths. “It’s about listening to the ocean – in a way we’ve never been able to before.”

This week’s deployment – just under two kilometres of fibre optic cable – marks the beginning of a pioneering experiment that could change how scientists study and protect marine life. Backed by a $1.5 million grant from Allen Family Philanthropies, the project aims to repurpose the global web of submarine telecommunications cables as a vast, real-time listening network for the sea.

If successful, the same infrastructure that carries the internet between continents could also carry the songs of whales, the creak of shifting ice, the distant rumble of underwater landslides – a constant, living chorus of the ocean itself.

The ocean’s hidden orchestra

The idea centres on a technique known as Distributed Acoustic Sensing, or DAS – a technology that turns ordinary fibre optic cables into a network of thousands of ultra-sensitive vibration sensors.

Inside each glass strand, pulses of laser light travel at nearly the speed of light. When something disturbs the surrounding water – a whale call, a propeller, a faint earthquake – the fibre flexes ever so slightly. These microscopic changes alter the pattern of the reflected light, allowing scientists to reconstruct exactly where and when the disturbance occurred.

“Think of it like a string stretched across the seafloor,” says Abadi. “If a whale calls a kilometre away, the cable feels that vibration. And because it’s continuous, we don’t just know that the sound happened – we know where it came from, and how it moved.”

Unlike traditional hydrophones, which detect sound from a single point, DAS can ‘hear’ along its entire length. The result is a dynamic, high-resolution map of underwater soundscapes – one that could span tens or even hundreds of kilometres.

The technology was originally developed for detecting seismic activity and monitoring pipelines. But in recent years, researchers have realised that the ocean’s constant hum – once considered background noise – is full of biological information. Whale calls, dolphin clicks, even the crackle of snapping shrimp can be detected with astonishing clarity.

The Southern Residents’ call

For Abadi and her team, the stakes are personal and local. Their initial test site lies within the range of the Southern Resident killer whales, a beloved yet critically endangered population that spends much of the year navigating the waters between Seattle and Vancouver Island.

These orcas are iconic in the Pacific Northwest – symbols of strength and community, but also of fragility. Their numbers have dwindled to just 74 individuals, threatened by food scarcity, rising water temperatures, and the relentless din of ship traffic.

“Sound is everything for orcas,” says Abadi. “It’s how they find food, communicate, navigate. But it’s also how they can be most easily disrupted.”

The waters of Puget Sound are often murky, making visual surveys unreliable. Orcas spend nearly all their time below the surface, leaving scientists dependent on sound to track their movements. Traditional hydrophones have helped, but they cover only limited areas.

DAS could change that. By linking the region’s existing fibre optic cables – many of which already criss-cross the seafloor – scientists could monitor vast stretches of ocean in real time.

“We hope to show that fibre optic cables can detect orca vocalisations,” Abadi says. “That would allow us to triangulate their positions and alert ships to slow down or steer clear. It could save lives – both animal and human.”

From the Sound to the world

The University of Washington team includes a diverse roster of co-investigators: Dr. William Wilcock of the School of Oceanography; Dr. Brad Lipovsky and Dr. Marine Denolle of the Department of Earth and Space Sciences; and Dr. Scott Veirs, founder of the nonprofit Beam Reach. Together, they’re blending expertise in acoustics, marine biology, and geophysics to explore how this technology might scale.

Beam Reach, which has long operated a network of hydrophones in the Salish Sea, will provide comparative data – a way to test how DAS stacks up against conventional listening systems. Graduate students Isabelle Brandicourt and Samantha Juber are analysing the acoustic data, teasing apart whale calls from the underwater noise of ferries, fishing boats, and waves.

If the trial succeeds, the implications are global. There are already more than 1.2 million kilometres of fibre optic cable beneath the world’s oceans. Repurposing even a small fraction could create a vast network of passive acoustic observatories – a planetary-scale “ear” attuned to the health of the seas.

“This project could lead to a global monitoring network that protects endangered species,” says Dr. Yuta Masuda, director of science for Allen Family Philanthropies. “It’s a way to understand not only where marine mammals are, but how they’re responding to human pressures and climate change.”

The trial will run for two years, capturing the rhythmic pulse of the Salish Sea across seasons. The researchers expect to detect everything from the songs of humpbacks to the mechanical rumble of cargo ships – a soundscape as complex as it is revealing.

For Abadi, the excitement lies not just in the data, but in what it represents: a new relationship with the ocean. “The sea is constantly speaking,” she says. “For so long, we just didn’t have the right instruments to listen.”

If all goes as planned, the team will not only decode the voices of the orcas but also build the foundation for a global acoustic observatory – a network capable of hearing life, movement, and change across the planet’s blue heart.

As the boat drifts near the San Juan Islands, the last of the morning fog begins to lift. Somewhere beneath the surface, an orca call echoes – low and haunting, a note that travels for miles. It’s possible, now, that the thin glass line resting on the seafloor has already heard it.

And for the first time, the ocean might finally be speaking through the same fibres that connect us all.