A reliable internet connection is something we take for granted – until it gets disrupted.

That disturbance may be caused by damage to an undersea cable, as UAE residents found to their cost early last month when cables in the Red Sea were severed and internet speeds slowed down.

Many companies across the world are ready to respond when undersea infrastructure is damaged by, for example, fishing gear or a ship’s anchor, which together account for about three quarters of incidents involving telecoms cables.

Undersea landslides, in which shifting rock or sediment, and technical faults may also damage subsea cables, or they may be harmed deliberately, although this is rare.

There are dozens of repair vessels dotted across the globe, ready to be activated in the event of an incident, although it is not cheap work, with ships reportedly costing many tens of thousands of dollars each day they are at sea.

Among the companies that operate them is Orange Marine, which has six cable repair ships at off the coasts of places including Sicily, the South of France and South Africa.

“We have contracts with many cable operators in various areas and the contractual obligation will be to be able to sail within 24 hours,” chief executive Didier Dillard said. “Most of the time you need to load spare cables. It can take one hour, [or] one day.”

A ship may have to sail for up to 10 days to reach the site of the damage, which may be identified by sending a pulse down a cable, with the length of time that it takes to travel pinpointing the fault.

Most cable damage occurs in waters no deeper than several hundred metres. Down around 2,000 metres, an ROV (remotely operated vehicle) is often used to locate the cable, cut it and lift sections to the surface. Repairs take place on board, with the insertion of a replacement section along with connectors, before the cable is returned to the seabed. To reduce the likelihood of damage, the cable may be buried, perhaps down to a couple of metres.

Dealing with damaged power cables can tak