How Norway is Building a $47B Tunnel That Floats Underwater

Added: 2026-06-03

[00:00:01]This fjord is 1,300 m deep. No bridge, no tunnel, nothing crosses it.

[00:00:08]Norway's main coastal highway stops seven times for a ferry every single time.

[00:00:17]Ferry's cancel in winter. People miss hospitals, children miss school.

[00:00:22]Norway's biggest problem.

[00:00:24]>> Norway's solution to this problem sounds physically impossible. A highway that floats 30 m underwater.

[00:00:31]>> The Sognefjord is 1,300 m deep. It swallows the English Channel whole.

[00:00:39]Two concrete tubes 30 m underwater. Cars drive through, ships pass above.

[00:00:47]Inside, a normal tunnel. Outside, floating in a fjord. Nothing like it exists.

[00:00:54]20 years of study. The physics works.

[00:00:57]The construction method still unanswered.

[00:01:01]21 hours, Kristiansand to Trondheim.

[00:01:05]Same distance in a straight line, 4 hours. Remove seven ferry crossings, cut 10 hours from the journey. That is the entire point.

[00:01:23]Norway has 1,190 fjords. The western coast is more water than land.

[00:01:29]The Sognefjord is deeper than most mountains are tall. No tunnel, no bridge, nothing.

[00:01:36]Ferry's cancel in winter. A canceled ferry means a 3-hour detour. For ambulances, lives lost. The widest fjords need 3-km spans. The world's longest suspension bridge, 2 km, impossible.

[00:01:52]>> Engineers looked at this crossing three questions. Can you bridge it? No. Can you float a tunnel through it? Nobody had ever tried.

[00:02:00]>> The tunnel under the Sognefjord would go 1,300 m deep. Rock pressure crushes machines there. Bridge, impossible.

[00:02:09]Subsea tunnel, impossible. Floating tunnel, never built.

[00:02:14]Norway chose the impossible one. Chief Engineer Arianna Minoretti. The floating tunnel is the only solution that actually works. Seven ferry crossings cost Norway billions annually. Lost time, delayed freight, failed emergencies. It pays back. Four crossing methods on the E39. Bridges, tunnels, floating bridges, and the one that doesn't exist yet. Two tubes, 30 m underwater, pontoons above, anchors below. Simple concept, impossible construction. The tunnel wants to float up. Anchor cables hold it at exactly [music] 30 m.

[00:02:54]1 m concrete walls, road inside, fjord water outside, three atmospheres of pressure.

[00:03:02]Pontoons hold the tunnel at depth. In a storm, they take the wave energy. The tunnel, nothing.

[00:03:09]Pontoon cables up, >> [music] >> anchor cables down. The tunnel hangs between them. 1 m error, unacceptable.

[00:03:17]>> This solves everything. It's too deep for a tunnel, too wide for a bridge, but because it floats below ship depth, the surface remains entirely undisturbed.

[00:03:27]>> Cruise ships here are 70 m tall. [music] Tunnel is 30 m down. Ships pass, never knowing. The Sognefjord crossing is 3.7 km of floating concrete tubes, 30 m underwater, never built before. Fresh air doesn't arrive naturally at 30 m depth. Fans run continuously. They never stop.

[00:03:52]Four fjords, four floating tunnels, each different depth, each different challenge. None of them built yet.

[00:04:06]The tubes are built on land, precast sections transported by barge, then submerged into the fjord. 200 m long, >> [music] >> 1 m concrete walls, reinforced steel inside. Built on land, launched into water.

[00:04:23]On land, conventional work, formwork, rebar, concrete. The challenge only starts when it hits the fjord. One waterproofing failure at 30 m, water fills the tunnel in minutes. Every centimeter must be sealed.

[00:04:40]Each section launches like a ship.

[00:04:43]Hollow concrete floats. Workers control it by cable. The fjord receives its tunnel.

[00:04:50]>> That launch is the most dangerous moment of the entire construction. A 200 m concrete tube entering the water or sinks at the wrong angle, the engineering tolerance is millimeters.

[00:05:06]>> Towed into position, then ballasted.

[00:05:08]Water fills internal tanks and lowers it to exactly 30 m depth. Fill the ballast tanks, it sinks. Adjust the water, depth adjusts. A 200 m tube controlled to centimeters.

[00:05:23]Joining two sections at 30 m depth under fjord pressure.

[00:05:28]The joint must be watertight instantly.

[00:05:32]Divers make the underwater connections.

[00:05:35]>> [music] >> Decompression limits their time. Every connection must be right.

[00:05:40]Sections joined. Pontoons attach above, anchor cables below.

[00:05:45]The tunnel hangs between them. Anchor cables in the Sognefjord go 1,000 m down.

[00:05:52]Divers can't reach there.

[00:05:54]ROVs make the connections.

[00:05:57]ROVs operate from the surface at 1,000 m depth.

[00:06:01]The fjord floor has never been worked on before.

[00:06:04]Fjords have currents. The tunnel sits in moving water.

[00:06:08]Anchor cables resist that force permanently, forever.

[00:06:14]Winter waves reach 4 m in Norwegian fjords. That force hits the pontoons.

[00:06:20]The tunnel cannot move 10 cm.

[00:06:24]>> Every winter brings storms like this.

[00:06:27]But 30 m below us, that tunnel won't budge. That is a 100-year guarantee.

[00:06:33]>> Ferry's fail. Roads close. The floating tunnel, once built, closes for nothing.

[00:06:39][music] It sits below the weather.

[00:06:42]Two tubes connected every 250 m.

[00:06:46]Incident in one, drivers evacuate to the other.

[00:06:49]Pressurized shafts to surface. Fire 30 m underwater. Suppression activates in 30 seconds. Smoke extraction 200 cubic meters per second. [music] While the floating tunnel is being designed, another E39 project is already being built right now.

[00:07:19]Rogfast.

[00:07:21]TBMs cutting rock 392 m below sea level.

[00:07:25]These same workers will eventually build the floating tunnel above them.

[00:07:29]An underwater roundabout 250 m below [music] sea level.

[00:07:34]The deepest road junction ever built.

[00:07:37]Inside a mountain, under a fjord. 10 million cubic meters of rock removed by drill and blast 392 meters down.

[00:07:47]Rogfast completes in 2033.

[00:07:51]27 kilometers, 392 meters deep, a dual carriageway under a fjord, under construction now.

[00:08:00]>> This isn't a plan, it's already happening. Right now, crews are digging 392 meters below this fjord.

[00:08:07]>> 4 meters of tunnel bored every day. 392 meters down, the floating tunnel will take even longer.

[00:08:17]Rogfast under construction. Floating tunnel still being engineered. The fjords have waited 10,000 years. Norway is patient. Waves hit the pontoons 10 times per minute. [music] In 100 years, 5 billion impacts. No precedent. Wave tank testing for 15 years. Scale models, simulations. Construction hasn't started because research isn't finished. Norway has earthquakes. Rare, but real. The tunnel must survive a magnitude five without leaking.

[00:08:52]A ship losing control above. Keel reaches 15 meters depth. The tunnel is at 30. 15 meters.

[00:09:01]A dragging anchor threatens the tunnel below. Concrete covers protect it, but no perfect answer exists. 25 [music] billion dollars for the Sognefjord crossing alone. Full program, 40 billion dollars.

[00:09:15]Engineering is the only problem.

[00:09:18]Parliament must approve. Construction can't start before late 2020s. [music] Completion, possibly 2040s.

[00:09:26]12 countries are watching Norway's research. The US, China, Italy. Everyone waiting for Norway to go first.

[00:09:35]>> They're designing something without precedent. No reference project, no data, no safety net. They are writing the textbook as they go.

[00:09:44]>> The fjords created Norway's isolation.

[00:09:47]The floating tunnel ends it. Ferry free, weather free.

[00:09:51]First time in history.

[00:09:57]>> [music] >> An ambulance waiting for a ferry in an emergency. That wait is up to 3 hours.

[00:10:15]Tunnel ends that. Bergen to Stavanger, 5 hours 30 today. After the E39, 2 hours 45.

[00:10:25]Fjord communities are economically isolated today. The tunnel reaches European markets in hours. $40 billion pays back. A student takes three ferries to university in Bergen today. After the E39, one road, no ferries.

[00:10:42]Norway's fjords are Scandinavia's most visited attraction. Ferry dependent today. After the E39, drive directly in.

[00:10:50]Norway is not building this for Norway alone. Chile, New Zealand, Canada, Scotland, all of them watching. Italy has Lake Como, Lake Maggiore. No bridge, no tunnel. Norway proves it. Italy builds next. China's Three Gorges has the same problem. Chinese engineers study this directly. Norway builds, China follows. Scottish lochs go deeper than 200 m. Norway proves the concept.

[00:11:19]Scotland has 10 sites ready. Norway patents every solution as it develops.

[00:11:24]Anchor system, pontoon design, joint connection. The world will license this.

[00:11:29]20 years of research, hundreds of millions spent into a technology that doesn't exist. Ferries are not enough.

[00:11:37]Patented in Britain in 1919, being engineered in Norway in 2025, 100 years between idea and reality.

[00:11:47]South Korea has a proposal, China has studies, [music] Italy has locations, Norway leads the race by a decade. This is what the tunnel replaces, a ferry in a Norwegian winter in a fjord everyday.

[00:12:10]Right now in 2025, [music] Rogfast under construction, floating tunnel research ongoing, Parliament approved, funding is next. Holsafjorden, 1.2 km, almost certainly the world's first floating tunnel, not the biggest.

[00:12:32]Right now in Oslo, engineers designing something never built. No textbook answers, no previous failure to learn from.

[00:12:49]Parliament approval late 2020s, [music] first tunnel possibly 2035, Sonya Fjord possibly 2045.

[00:12:57]Inside, it feels like any tunnel. Two lanes, lights, normal driving, 30 m underwater.

[00:13:05]>> Riding the ferry this tunnel will replace, I look at the water that will one day cover a concrete tube of cars.

[00:13:11]The captain says retired by opening day, his kids will be the first to drive it.

[00:13:15]>> Holsafjorden, 1.2 km, almost certainly first, not the biggest challenge.

[00:13:22]Workers trained before construction is even approved, because when approval comes, the workforce must be ready that day. The Sognefjord in winter, in storms, in ice. The tunnel operates through all of it for 100 years.

[00:13:38]Patented 1919, built possibly 2035.

[00:13:43]21 hours today, 11 hours after the E39.

[00:13:48]Seven ferries today, zero when the floating tunnels open.

[00:13:52]>> Norway isn't building a tunnel. It's 10,000 years if they just have to invent it.

[00:14:05]>> 1,300 m deep, tunnel floats at 30. Above it, 1,270 m of nothing. Pontoons and anchor cables. That family crosses by ferry every day. In winter, it cancels. 3 hours around. The tunnel changes everything. 400 m of granite above water. 1,300 m of depth below. The tunnel floats 30 m down. Ferries still running. Fjord still uncrossed. Tunnel being designed. In 10 to 20 years, this all changes.

[00:14:41]>> A century after a British engineer patented the floating tunnel, Norway is finally building it because they're done with winter ferries.

[00:14:49]>> $47 billion, never built before. Four fjords. Changes infrastructure worldwide. Not if, when.