Rather than being a rare occurence, damage to the cables are rather common. Currently, there are more than 50 repairs a year in the Atlantic alone.

First, the damage must be located in the cable. Electrical measurements like spread-spectrum time-domain reflectometry can be used to estimate the location of the break in a matter of miliseconds. Once the break is located, a repair ship is sent to the location. Depending on the makeup of the sea bed, different types of grapples will be sent down. In very deep waters, the cable will be cut after the grapple has attached, and the crew will repair the cable above water in sections. In less deep waters, the repair can be done by simply pulling the cable up out of the water without cutting it. In very shallow waters, a submersible can be used to repair the damage.