Plans for an underwater high-speed train linking continents are being slammed by critics, who warn it could devastate oceans and amount to an environmental crime

On a wet, windswept morning in January, Lea Kovic - an engineer who has since become an activist - stood at the end of an Atlantic pier, watching the surface as though she was trying to hear a message in the waves. Fishing boats lurched on the swell, their engines swallowed by the ocean’s roar. Beneath that steel-grey water, well below the gulls and the froth, governments and technology giants are eager to push a bullet train through the dark.

In her mind’s eye, it is already there: a glass-and-steel conduit cut into the seabed, with ultra-fast capsules streaking past whales at 600 km/h. Fares marketed on the promise of New York–London in under two hours. A “new Silk Road” for a world that refuses to wait.

Then she adds, almost under her breath: “Once you carve a highway into the ocean, you don’t get to take it back.”

Supporters describe the scheme as the future.

Opponents describe it as an environmental crime.

Underwater train: a high-speed tunnel plan under the spotlight

At first glance it reads like pure science fiction: a high-speed underwater train running inside a sealed tube, spanning continents through pressurised tunnels laid along the ocean floor. Promotional visuals show streamlined pods gliding through neon-blue water, passengers sipping lattes while sharks drift past outside.

The sales pitch is polished. No jet lag. Lower-carbon travel. A fresh chapter of global connection. For politicians who want to cut aviation emissions without putting the brakes on growth, it is an enticing proposition. For financiers, it has the sheen of the next moonshot.

Yet away from the glossy renderings, marine biologists, small island states and Indigenous coastal communities study the same plans with something far closer to fear.

A leaked feasibility assessment for an Atlantic alignment reportedly traced a tunnel route directly through established migration corridors used by humpback and fin whales. On the page, it is a neat line. In the water, it overlays a living thoroughfare already busy with bodies and songs.

Near Iceland, researchers have started modelling the sort of constant low-frequency vibration such trains could generate. Early simulations point towards a long-lasting noise “halo” reaching hundreds of kilometres - a kind of mechanical haze that never properly lifts.

Fishers interviewed around possible landfall locations speak openly about what construction would mean: dredging, blasting, concrete bases, and relentless heaps of rock and steel. One man simply shrugged and said, “If they do this, my son will probably be the last in our family to fish here.”

On land, we are accustomed to bulldozing through, tunnelling under, and building over. The scars our infrastructure leaves are obvious; we pass them daily and eventually stop seeing them. Beneath the surface, harm is far easier to conceal.

That invisibility is precisely what unsettles critics. A tunnel bored through seabed rock in the deep, beyond daylight, is not merely an inert passage. Construction can set off seismic shocks, stir sediment plumes that drift with currents, and embed a permanent chain of maintenance nodes, cables and power supplies. Each element can introduce noise, heat and chemical runoff into ecosystems that evolved under near-total stability.

A high-speed underwater train doesn’t just connect continents; it locks industrial activity into the very places we still barely understand.

The hidden cost of “progress”

If the mega-project advances, the first unmistakable sign will not be a sleek capsule - it will be fleets of vessels. Survey ships towing sonar arrays across the seabed. Drilling platforms punching test holes into deep sediment. Barges dropping sensors and explosives for seismic mapping.

In Portugal and Canada, campaigners are already watching for these early steps using binoculars and open-source vessel tracking. They have dubbed it “the creeping phase” - the quiet window in which nothing has been formally authorised, yet the ocean is steadily converted into datasets and profit forecasts.

Activists on the ground offer a practical rule of thumb: follow the small agreements. Environmental impact statements. “Temporary” test platforms. Support ports. That is often where the point of no return starts.

Many of us still picture the sea as limitless and self-repairing. We dump, dig and blast, trusting the tides to scrub away the trace. Then we act shocked when coral reefs bleach, fish populations collapse, and coastal storms hit harder year after year.

With the underwater train, the usual error is to treat it only as a cleaner substitute for planes. On paper, fewer transatlantic flights sounds like a climate win. Campaigners argue that framing is misleading. A vast, permanent tunnel network would be layered on top of existing strains: deep-sea mining, container shipping, offshore drilling, plastic pollution.

Let’s be frank: almost nobody reads those three-hundred-page environmental assessments from cover to cover. That is how dangerous shortcuts slip through.

The most uncompromising opponents refuse to soften their language. To them, this is not brave innovation, but a late-stage effort to keep extending an economic model that has already collided with planetary limits.

“This is not transport. This is colonisation of the deep,” says marine ecologist Dr. Rahul Menon. “We’re taking a damaged relationship with the land and exporting it to the oceans, which are already on life support.”

They have also begun sharing internal slides from investment presentations, including one bullet point that reads, “Unlocking undersea real estate value.” The phrase hits like a blow: oceans reduced to an “asset” column in a spreadsheet.

• Noise: an unbroken low-frequency rumble disrupting whales and fish.
• Light: artificial illumination from stations and maintenance hubs spilling into dark-water zones.
• Chemicals: lubricants, paint particles and microplastics feeding into currents.
• Heat: warming plumes near power systems altering local habitats.
• Access roads and ports: fresh coastal scarring that can invite further industrial build-out.

What world are we really building?

Seen from a distance, the underwater train is as much about our relationship with speed as it is about engineering. A 90-minute Atlantic crossing sounds exhilarating - and it also assumes we should be constantly reachable, permanently switched on, always moving faster than our nervous systems can comfortably handle.

For young professionals in global cities, the fantasy of breakfast in Paris, lunch in New York, and dinner back home is hard to resist. For someone in a coastal village watching yet another “strategic hub” appear along their shoreline, it can feel like another person’s dream bulldozing through their low tide.

Behind the noise sits a quieter question: who is this really meant to serve?

We all recognise the pattern: a dazzling new technology lands in the feed and, for a moment, we picture life becoming smoother, smarter, easier. Then reality intrudes. Someone carries the cost. Often it is not the person scrolling headlines on a new phone, but a community that never asked for the “upgrade” in the first place.

Opponents say the underwater train is repeating the same story. Those likely to be affected most - Indigenous fishers in the Arctic, small island states in the Pacific, and coastal towns from Ireland to Morocco - are still battling for genuine participation. Their questions are pointed: What becomes of our fisheries? Who is responsible if something fails 4,000 metres down? Who gets to decide what counts as “acceptable damage”?

Engineers respond with soothing charts and worst-case scenarios shaded in gentle colours. Politicians speak about “balancing” protection with growth. Meanwhile, the phrase opponents keep returning to - raw, emotive, and difficult to dismiss - is environmental crime.

• Is an underwater train really an environmental crime?
  Critics choose that wording to stress intention and scale. This would not be a small error; it would be a deliberate choice to industrialise fragile, poorly understood ecosystems for profit, despite decades of warnings about ocean health.
• Could such a project ever be truly sustainable?
  Supporters say robust safeguards, cleaner construction practices and strict marine zoning could limit damage. Opponents argue that certain areas - deep-ocean trenches and major migration routes - should be treated as off-limits, not “optimised”.
• What about jobs and economic growth?
  Proponents promise tens of thousands of high-tech roles and revived port cities. Coastal communities reply that short-lived construction surges can leave behind hollow infrastructure, while traditional livelihoods fade away quietly.
• Would it reduce aviation emissions?
  Perhaps - but only if it genuinely replaces long-haul flights rather than creating extra demand. Some climate researchers caution that mega-projects like this often “stack” on top of existing travel instead of substituting for it.
• Is there a way to slow this down?
  Activists point to strategic levers: international ocean treaties, legal action invoking the rights of future generations, citizen monitoring of early survey activity, and pressure on the media to cover the seabed with the same urgency as the sky.

Key point	Detail	Value for the reader
Deep oceans aren’t empty	They’re dense with life, migration routes, and fragile ecosystems.	Helps you see the train route as a living space, not just a line on a map.
“Green” labels can mislead	Cleaner than planes doesn’t mean harmless when added to existing pressures.	Gives you a sharper filter for future mega-project promises.
Public scrutiny still matters	Survey ships, impact studies, and local hearings are leverage points.	Shows where individual and community action can still change the story.

FAQ:

• Question 1 Is an underwater high-speed train technically feasible today?
• Question 2 How would the tunnels be built on the seabed?
• Question 3 What are scientists most worried about ecologically?
• Question 4 Who is pushing hardest for this project behind the scenes?
• Question 5 What can ordinary citizens do if they’re concerned?