Maybe they’re trying to disrupt our communications infrastructure before mounting a land-based assault. Maybe it has something to do with electromagnetic fields.

There’s disagreement as to why, exactly, sharks occasionally gnaw on submarine communications cables. Though per-mile prices for installation change depending on total length and destination, running a cable across the ocean invariably costs hundreds of millions of dollars. Cables located at shallow depths are buried beneath the ocean floor using high pressure water jets. The size difference is related to simple vulnerability-there’s not much going on 8000 feet below sea level consequently, there’s less need for galvanized shielding wire. The diameter of a shallow water cable is about the same as a soda can, while deep water cables are much thinner-about the size of a Magic Marker. It’s more than a matter of dropping wires with anvils attached to them-the cables must generally be run across flat surfaces of the ocean floor, and care is taken to avoid coral reefs, sunken ships, fish beds, and other ecological habitats and general obstructions. The cables are installed by special boats called cable-layers. In total, they are hundreds of thousands of miles long and can lie 8000 meters below the surface-as deep as Mount Everest is tall. More than 95 percent of international data is transmitted by wires at the bottom of the ocean called submarine communications cables. Cable installation is slow and expensive.

Here are 10 things you might not know about the internet’s system of undersea cables. The rest of it can be found in the coldest depths of the ocean. But what we see is just a small part of the physical makeup of the net. From telephone poles suspending bundles of cable to signs posted warning of buried fiber optic lines, we are surrounded by evidence that at a basic level, the internet is really just a spaghetti-work of really long wires. In describing the system of wires that comprises the internet, Neal Stephenson once compared Earth to a computer motherboard.

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