Cable repair

Cables can be broken by fishing trawlers, anchoring, undersea avalanches and even shark bites. Breaks were common in the early cable laying era due to the use of simple materials and the laying of cables directly on the ocean floor rather than burying the cables in trenches in more vulnerable areas. Cables were also sometimes cut by enemy forces in wartime. Cable breaks are by no means a thing of the past, with more than 50 repairs a year in the Atlantic alone,[9] and significant breaks in 2006 and 2008.
To effect repairs on deep cables, the damaged portion is brought to the surface using a grapple. Deep cables must be cut at the seabed and each end separately brought to the surface, whereupon a new section is spliced in. The repaired cable is longer than the original, so the excess is deliberately laid in a 'U' shape on the seabed. A submersible can be used to repair cables that lie in shallower waters.
A number of ports near important cable routes became homes to specialised cable repair ships. Halifax, Nova Scotia was home to a half dozen such vessels for most of the 20th century including long-lived vessels such as the CS Cyrus West Field, CS Minia and CS Mackay-Bennett. The latter two were contracted to recover victims from the sinking of the RMS Titanic. The crews of these vessels developed many new techniques and devices to repair and improve cable laying, such as the "plough