At least a couple times here, I've mentioned undersea telecommunications cables. Those are, if you don't know or haven't been paying attention, the thing that permits digital data, such as the Internet, to work across continents. Virtually all overseas communication relies on them, and most countries with a sizable population have not just one or two but several different cables running to them so that if one is cut for whatever reason, they're not going to suffer a total blackout. (By 'most', we are of course referring to 'the countries that can afford to pony up for those cables; the poorer countries have fewer connections and are more vulnerable to an outage.) They're roundabout three inches in diameter on average, and laid using special ships designed to steadily ease it overboard as they cross from one land base to the other. There are also ships designed to find and repair damaged cables when that need arises.
But odds are you probably don't know where those cables exactly, well, are. Today I fix that. This link goes to an interactive map showing all undersea cables currently in operation, and where each of them link up, as well as when it was laid and, in case it means anything to you, who owns it.
They may appear to resemble the tangled mess behind your desk (or at least under mine), but that's just the scale talking.