Cable ships that criss-cross the world's oceans, laying lines to facilitate communications, have existed since the 1850s. But in 1961 AT&T launched what was then considered the world's most modern cable layer, the C.S. Long Lines, which could hold almost 4000km of cable at a time.
During its first two decades of operation starting in 1963, C.S. Long Lines was responsible for laying over 64,000km of cable around the world, including multiple trips across the Atlantic and Pacific Oceans. And by the time AT&T sold it in 1997, it had been used in 23 missions including the laying of the first modern transatlantic fibre-optic cable in 1988. [YouTube]