Human activity causes the vast majority of underwater cable damage.
You may have heard this week that Google's ponying up big money to prevent sharks from gnawing its undersea fibre-optic internet cables. Yeah, sharks do occasionally bite a cable, but they haven't exactly developed a taste for them.
In reality, as enticing as the idea of the behemoth corporation struggling to fend off toothy internet-eaters is, the most pressing threat to our underwater infrastructure is (surprise surprise) human activity.
The source of the shark story is a comment made by Dan Belcher, a Google cloud product manager, at a recent Google Cloud Roadshow event in Boston, as reported by Network World. Belcher reportedly said that Google "goes to great lengths to protect its infrastructure, including wrapping its trans-Pacific underwater cables in Kevlar to prevent against shark attacks."
It's true Google co-owns some 5,000 miles fibre-optic cables spanning the Pacific, and recently announced it's investing alongside five other companies in a second trans-Pacific cable system called FASTER. It's also true the company, and all cable owners, invest a ton of time and money into protecting the notoriously vulnerable submerged infrastructure.
"All submarine equipment providers support a variety of cables with different degrees of hardening that depend on the cable depth, and protect against a number of external aggressors like ship anchors/trawlers/fishing, seabed corrosion, and yes, even sharks," a Google spokesperson told me in an email. "Cable ships are on standby around the world and dispatch to fix cables when they go down."
So, yeah, new cables are hardened and protected by a mixture of polyethylene (a hard plastic) and steel wire, and a side effect of that casing is that sharks won't go chomping through them. But that's not the primary reason they're hardened.
Some 70 percent of cable faults are caused by ship anchors and fishing trawlers that inadvertently snag a comms cable. Another 10-15 percent of damage is from natural disasters like earthquakes, underwater landslides, or tidal currents dragging a line over the rocky surface, according to the International Cable Protection Committee.
The shark problem is actually something of an urban myth in the submarine cable industry, born after a 1987 New York Times report that a shark bit into a Canary Islands cable line, which was reportedly confirmed by tooth marks embedded in the cable, though some experts remain skeptical.
That was followed by fun speculation that the high-voltage power emitted attracts fish who mistake the electric fields for distressed fish (the Times called it an "inexplicable taste")—a theory that still lives on today.
"I've talked to people in the subsea industry about this, because it seemed like an urban legend when I heard it," Tim Stronge, a cable expert at telecommunications research firm TeleGeography, told me in an interview.
"I tried to get to the bottom of it … they swore they saw shark teeth," he said. "But why they're attracted to fibre I don't know. And I very much doubt people in the industry actually know."
After the incident, it became commonplace to manufacture armoured cables, reinforced with a metal sheathing and in some cases, a Kevlar-like material as well.
Cables in shallow waters or near the shore—i.e. more likely to get snagged by an anchor or fishing trap—starting being buried under the seabed for extra protection. That's about when shark bites stopped being a problem.
The inside of a fibre-optic cable is extremely fragile, made of glass or plastic fibers that are generally encased in plastic and then secured with steel. Deep sea cables are about as thick as a garden hose, whereas cables in shallow water and closer to land are closer to the size of a grapefruit, at least, explained Stronge.
The reports circulating the blogosphere this week include a YouTube video of what clearly looks like a shark mouthing at an undersea cable, suggesting there's been more recent attacks.
"It seems legit to me but who knows what type of cable that is," said Stronge. "It couldn't have been an electrical cable." The video's dated from 2010, before Google owned any undersea internet infrastructure.
There are two different types of submarine cables crossing the ocean floor. One transmits electricity and the other, communications: telephone, fax, internet, and so on. Since the late 80s to early 90s, all communications cables have been fibre optic, rather than old copper wires. (Side note: another cause of cable damage are thieves mistaking fibre optic lines for these 60s-era lines; there's a lot of money to be made from reselling the copper.)
Sharks or no, maintaining the vast network of submarine communications cables is a daunting task, and an extremely crucial one. This submerged network carries some 99 percent of international communications, living up to its nickname as the backbone of the global information economy.
It's also an expensive task. After years of being, as Wired once put it, "poorly armored, rarely patrolled and only occasionally monitored," there's now an entire industry devoted to monitoring and repairing the cables, which break some 200 times a year. Dozens of ships are floating in waters around the world, essentially on standby, waiting for a rupture.
The owners of the submarine cable lines—major international telecom companies and now Google and Facebook as well—pay big money for this marine maintenance fleet. "It's almost like they have to purchase an insurance policy," said Stronge.
There's an annual payment, plus an additional $1-2 million per repair, he said. As a co-investor of the FASTER line, Google will have to pony up big money to protect its internet system.
"A shark can bite something," said Stronge. "But there are much greater problems under the sea for fibre-optic cables."