About 99% of the world's internet data is carried through high-capacity fiber-optic lines that are positioned under the sea. Nearly 750,000 miles of these underwater cables connect countries across the planet's vast oceans. So, how do those cables stay intact and how do we avoid breaking those underwater internet cables all the time? For example, ship anchors break undersea internet cables all the time. While much less common, shark bites can sever undersea cables, as well, though they make up merely 1% of all damage to those cables.