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A deep-sea 'emergency service' keeps the internet running

Ninety-nine percent of the world's digital communications rely on subsea cables. Fixing them keeps us all connected – and has changed our understanding of the ocean.

However, "for the most part, the global network is remarkably resilient," says Mike Clare, the International Cable Protection Committee's marine environmental advisor who researches the impacts of extreme events on submarine systems. In deep waters, giant underwater ploughs dig trenches for the cablesTo repair the damage, the ship deploys a grapnel, or grappling hook, to lift and snip the cable, pulling one loose end up to the surface and reeling it in across the bow with large, motorised drums. The damaged section is then winched into an internal room and analysed for a fault, repaired, tested by sending a signal back to land from the boat, sealed and then attached to a buoy while the process is repeated on the other end of the cable.

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