A cable layer or cable ship is a deep-sea vessel designed and used to lay underwater cables for telecommunications, electric power transmission, or other purposes. Cable ships are distinguished by large cable sheaves for guiding cable over bow or stern or both. Bow sheaves, some very large, were characteristic of all cable ships in the past, but newer ships are tending toward having stern sheaves only, as seen in the photo of CS Cable Innovator at the Port of Astoria on this page. The names of cable ships are often preceded by "C.S." as in CS Long Lines.
The first transatlantic telegraph cable was laid by cable layers from 1857–58. It briefly enabled telecommunication between Europe and North America before misuse resulted in failure of the line. In 1866 the SS Great Eastern successfully laid two transatlantic cables, securing future communication between the continents.
Modern cable ships
Modern cable ships differ greatly from their predecessors. There are two main types of cable ships: cable repair ships and cable-laying ships. Cable repair ships, like the Japanese Tsugaru Maru, tend to be smaller and more maneuverable; they are capable of laying cable, but their primary job is fixing or repairing broken sections of cable. A cable-laying ship, like the Long Lines, is designed to lay new cables. Such ships are bigger than repair ships and less maneuverable; their cable storage drums are also larger and are set in parallel so one drum can feed into another, allowing them to lay cable much faster. These ships are also generally equipped with a liner cable engine (LCE) that helps them lay cable quickly.