The subsea cables that carry 99% of global internet traffic

Ted Stevens was right.

Well, kinda.

The Republican Senator from Alaska, Stevens became the avuncular avatar of tech illiteracy in June 2006, thanks to a garbled speech during a Senate debate on net neutrality.

“The internet is not something that you just dump something on,” Stevens rambled. “It’s not a big truck. It’s a series of tubes. And if you don’t understand, those tubes can be filled. And if they are filled, when you put your message in, it gets in line and it’s going to be delayed by anyone that puts into that tube enormous amounts of material.” (1)

The octogenarian Stevens was lambasted for his rudimentary grasp of the internet and his simplistic explanation of its mechanics. “A series of tubes” became shorthand for the kind of digital ignorance characterised by bamboozled boomers. But ultimately, Stevens was correct. In a roundabout way, at least. Sorta.

To Stevens’ overarching point, we still think of the internet as a glistening magic machine lurking in the ether. When we want to Google something, or scroll TikTok, or stream New York Yankees games an ocean away, we click a few buttons and – voilà – instant gratification. The process is so familiar, the world wide web so ubiquitous, that we rarely contemplate its inner workings. How all this happens scarcely warrants thought. But the physical infrastructure that underpins the internet is just as interesting as the internet itself. And, again, Senator Stevens was onto something.

You see, even as superstar satellites capture the zeitgeist, 99% of the world’s international digital communications flow through subsea fibre optic cables, which are cheaper, quicker and possess more capacity. (2) Beneath the earth’s oceans and seas, more than 600 such cables – as thick as a garden hose, encased in copper or aluminium, and coated with tar – lurk as the backbone of the internet and, by extension, the modern world. (3) More than 1.3 million kilometres of underwater cables enable $3.65 quadrillion in digital transactions every year, boggling the mind in their importance to our very existence. (4) (5)

Crucially, most computational tasks – that aforementioned Google search, say, or simply receiving email – rely on fibre optics: a process whereby electronic data is converted into light signals, passed through thin glass strands encased in cables, boosted by lasers and photonic repeaters, then reconverted upon arrival. Where that journey requires international connectivity – streaming that Yankees game from London, for example – those fibre optic cables traverse vast subsea networks. A European prompt requiring an American answer nearly always obtains it via submarine tubes, and the same is true for almost all international permutations – global digital communication beholden to analogue plumbing.

That plumbing hearkens back to the gilded age of telegraphy. Indeed, many of the current subsea internet cable routes map directly onto those of international telegraph lines, pioneered in the 1850s. The first transatlantic fibre optic cable, TAT-8, was laid in 1988 as the nascent hardware outperformed satellites. (6) Costing $335 million, and linking the US, UK and France, TAT-8 greatly increased connectivity between those nations and turbocharged Tim Berners-Lee’s development of the world wide web. (7)

Other subsea fibre optic cables followed soon thereafter, spearheaded – and ostensibly owned – by major national telecoms operators. In the 1990s, amid the internet boom, fledging tech juggernauts typically rented bandwidth on those subsea cables from telecoms behemoths like AT&T. As demand grew, though, a new class of emerging web powerhouses – Amazon, Meta, Alphabet, et al – ventured to build their own subsea internet cables. However, given the exorbitant cost of each cable – between $300 million and $400 million – consortia were convened to fund new projects, and that model is still popular today. (8)

Take Amitié, the latest transatlantic cable. Funded by Meta, Microsoft and others, the cable carries 400 terabits of data per second – 400,000 times faster than the fastest home broadband you can ever hope to purchase. (9) Such ungodly capacity is not a mere luxury, either. So much capacity is required, in fact, that Meta and Microsoft partner on other subsea internet cables, including the $1 billion 2Africa link between Europe, Africa and Asia, which has enough power to download 7,500 HD movies from Netflix in an instant. (10)

Whether a few private companies should dominate such pivotal pieces of infrastructure is, of course, a highly contentious debate. Governments are typically involved in cable consortia, often providing grants to aid connectivity in internet black spots, but with billions spent on subsea digital infrastructure each year, private enterprise will always fuel the vanguard. Only the insatiable appetite of consumers, and thus, the demand felt by content providers, is strong enough to spur development at an adequate pace.

Practically, however, the deployment of that spend is often slow, deliberate and surprisingly dependent on physical graft. Only 27.3% of the world’s seafloor has been mapped in detail, complicating cable design and planning. (11) Regulatory approval is required to lay new cables, with consortia shopping for cheaper deals and more lenient conservation rules. Just a handful of companies – SubCom in the US; NEC in Japan; Alcatel in France; HMN Tech in China; and Prysmian Group in Italy – dominate the manufacture of subsea internet cables, while only 50 or so specialist ships are equipped to lay the finished product. (12)

That process – unspooling vast quantities of cable from onboard tanks – has changed very little since the 1850s, when telegraph lines were first installed. (13) Sure, installation ships have been gradually upgraded, and they now use GPS to position and lower cables, but the methodology still contains a fair amount of trial and error. In shallow water, where ship traffic is higher, cables are often buried beneath the seafloor. But at greater depth, where ships rarely roam, cables often lie on the seabed, unburied. Regardless, laying a subsea internet cable costs, on average, between €1 million and €2 million per kilometre – a gargantuan sum given the sheer size of ambitious modern projects. (4)

Moreover, in keeping with senator Stevens’ motif of clogged tubes, things often go awry with these precious subsea internet cables. The typical lifespan of a cable is regularly quoted at 25 years, but they are often compromised well before that term. (14) Every year, indeed, up to 200 damage events impact the web’s underwater infrastructure. (2) Around 86% of those events are attributed to fishing and anchoring, where bad weather or choppy currents lead vessels to drag their anchors. A further 7% of cable damage is caused by geological events, including volcanic eruptions and submarine landslides, while 4% can be traced to abrasion and 3% to plant failure. (15) 

Whales and sharks feasting on subsea internet cables is largely the preserve of urban legend and science fiction. However, in 2014, a shark did nibble on a Google underwater cable, with video footage confirming the incident. Google reinforced certain cables with a Kevlar-like matting, but reports of similar incidents are vanishingly rare. (16)

Generally, such cable damage goes unnoticed by end users – chiefly due to backup lines creating redundancy and traffic being rerouted by automated algorithms triggered by signal loss. (17) Historically, however, cable damage has led to prolonged, isolated internet outages. In 2007, for example, cut cables produced three months of internet disruption in Vietnam. (18) Similarly, in 2011, the Tōhoku earthquake and tsunami became synonymous with nuclear meltdowns at a plant in Fukushima, Japan, but a submarine landslide also destroyed seven transpacific and intra-Asia internet cables, causing extensive disruption. (19) (20)

Japan, of course, is an island nation, and those are obviously the most dependent on subsea cables for internet connectivity. Poor island nations face an even more perilous plight, relying – in some cases – on a singular cable due to unequal distribution influenced by capitalism, trade and geopolitics. When that cable breaks, the impact can be devastating – to the economy, education and general quality of life. In January 2022, for instance, a volcanic eruption under the Pacific Ocean knocked out Tonga’s lone incoming internet cable, and full rectification took 18 months. (21)

When such incidents occur, the delicate repair process falls into the hands of an even smaller cohort within the minuscule subsea internet cable community. Worldwide, there are less than 25 specialist repair ships, dotted strategically in each ocean, moored while awaiting job alerts. (22) When a cable is damaged, small crews sail out – often for days at a time – to locate the pipe in question. Ironically, repair ships do not have internet access in the furthest ocean reaches, and capturing the stricken cable can take up to a dozen attempts. Further, once it is brought aboard, said cable is spliced, tested and re-submerged – a painstaking process requiring patience and precision. (23)

Globally, less than 1,000 people are trained to repair subsea internet cables in this manner. (24) Typically, that resource has been adequate, but multiple cable errors happening simultaneously puts major strain on a stretched system. That, in turn, often leads to prioritisation, with backlogs occasionally forming, contributing to delays. In 2023, for instance, the average subsea internet cable repair time was 40 days – a wait often prolonged by intra-consortia squabbles over the burden of maintenance. (5)

Given the scarcity of repair resources, how intrinsic subsea internet cables are to modern life, and the ease with which they can be damaged, it is sadly inevitable that the seafloor is often considered the next great theatre of war. The United Nations Convention on the Law of the Sea (UNCLOS) 1982 encourages states to enact domestic laws making it illegal to wilfully break or injure submarine cables, but bad actors inclined to contravene international law would seemingly have little regard for such declarations – especially when it is relatively easy to cover up faux ‘accidents,’ such as dropped anchors, at sea.

In the murky world of geopolitics, then, where the fog of war thickens every day, subsea internet cables are conspicuous as bottlenecks of vulnerability. Depending on the circumstances, entire countries could be disconnected from the internet and the essential systems that rely on it with a single strategic cable cut. And to malevolent minds, that is a tantalising lever.

Rightly or wrongly, two pariah states spring to mind amid such dystopian possibilities: Russia and China. The former has reportedly shown a willingness to strategically recruit anchor-dragging ‘freelancers,’ (17) while the latter has been accused of similar shenanigans – plus cable surveillance – in its struggle with Taiwan. Moreover, just this year, China invested in a new tool that can cut cables up to 4,000 metres below sea level – a depth rarely reached by commercial vessels. (25) 

In such a high stakes arena, some countries seem more vulnerable than others. For example, 17% of global internet traffic goes through Egypt, which is connected to 16 different subsea internet cables. (26) Such chokepoints create outsized zones of vulnerability, increasing the hypothetical risk of attack by bad – or coerced – actors. 

There is little actual evidence of state-sponsored sabotage, however. Those pondering subsea warfare may be deterred by the interconnectedness of global financial markets and digital services routed internationally. They, too, would be impacted by large-scale internet cable damage, which could amount to self-sabotage. Nevertheless, many major powers continue to enact contingency plans, including the US, which has two ships on permanent standby to expedite complex repairs, and NATO, which recently upped its military presence in the Baltic Sea. (27) (28)

The direction of travel seems clear, then, with subsea internet cables gaining importance in myriad socioeconomic and geopolitical spheres. According to some projections, $13 billion will be spent on subsea cables between 2025 and 2027, compared with $6.6 billion between 2022 and 2024. (5) The so-called ‘hyperscalers’ – Meta, Microsoft, Amazon and their ilk – are increasing their cable demands by as much as 60% per year, according to SubCom CEO David Coughlan. (9) And with the inexorable appetite for AI compute, further subsea development will be required to meet demand.

To that end, the hyperscalers are increasingly keen to invest in their own cables – a desire analogous to their mooted interest in putting data centres in space as room on earth runs out. (29) In February, Meta launched Project Waterworth, which, at 50,000 kilometres, will become the world’s longest subsea internet cable, connecting five continents at a cost of $10 billion. (30) (31) Waterworth is the most ambitious – and most expensive – subsea internet cable project ever pursued by a single financing entity, and if it succeeds, other private juggernauts will follow suit.

Still, there are valid concerns among subsea cable repair firms that the hyperscalers are more inclined to throw money at new lines, increasing backup protection, rather than mending existing broken infrastructure. (32) To Meta, $10 billion is a drop in the ocean (no pun intended), and it is often easier to green-light installations than navigate the complicated politics of maintenance. The zeal for growth relegates repair, looming as an existential threat to the tiny band of maintenance specialists.

Indeed, the subsea internet cable repair industry has often been accused of a secretive, clandestine culture that hurts its own prospects of long-term sustainability. Subsea cable repair requires a very specialist skillset, and many existing experts are middle-aged or older, raising concerns about the ongoing transfer of institutional knowledge. The recruitment of future generations is often hampered by an insular ethos, with minimal public relations outreach failing to inform people these jobs exist, much less entice them to get involved. (22)

Similar entropy threatens the physical vessels upon which those repair specialists rely. Many of the world’s two dozen subsea cable repair ships are decades old, approaching the end of their efficient working life. As such, analysts warn that, by 2040, roughly 20 new ships will be needed to replace retiring vessels and meet growing demand. (33) However, with large ships costing up to $300 million to build and operationalise, many hyperscalers opt instead to simply lay their own proprietary cables for a similar amount. (34)

The onus should, perhaps, be placed on the cable-handling companies – SubCom, Alcatel, HNM Tech, Prysmian and others – to reinvest their profits into the building of new repair ships. And that would seem to be a prudent growth strategy for those firms, logically. However, laying new cables provides far more predictable revenue, compared to more sporadic, retainer-based repair work, leading shareholders to worry about returns on investment.

Overall, then, subsea internet cables face a paradoxical future – exponential investment stimulating buzz, but an imbalance in how that capital is skewed towards construction rather than maintenance dividing a parochial industry. In theory, as time goes on, more cables will be laid, increasing redundancy and rerouting options while making cable damage less impactful. But until bottlenecks, inequities and chokepoints are reconciled for mutual benefit – with public involvement, where necessary – optimism should be reserved.

Ultimately, Ted Stevens was right – if you squint hard enough. Keeping those tubes unblocked and unbroken is fundamental to global prosperity, cohesion and survival. But as for ensuring new tubes are built, and that everyone has fair access to them? Well, that will be a defining story of our time; the ending of which is undetermined.

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