Nearly 100 percent of international data crosses the ocean via undersea cables. They're only about three inches in diameter, but they span entire oceans. Plows dig grooves in the sandy ocean floor, lay the cables in, and the current buries them; some are buried as deep as Mount Everest is high.This seems insane—it is insane—but we've actually been using ocean-spanning cables since 1866, when the first successful trans-Atlantic telegraph line was laid. In 1956, we started making international phone calls via deep sea cables. Today, there's a system of nearly 300 undersea cables that transport our data.Oh, and to answer your potential followup question: Even if you're using wifi or phone data, it eventually reaches a physical cable and, if need be, sprints across the ocean.