Still, a few voices now call for stronger global mechanisms and even military action to protect the cables against future malicious activity by states, saboteurs or extremists.

"The infrastructure that underpins the internet – these undersea cables – are clearly vulnerable," said Rishi Sunak, a British member of Parliament and champion of more vigorous action to protect submarine networks. "They underpin pretty much everything that we do."

Undersea cables conduct nearly 97 percent of all global communications, and every day an estimated $10 trillion in financial transfers and vast amounts of data pass through the seabed routes. Satellites, once crucial but now limited in speed and bandwidth, handle only a tiny percentage of global communications.

As reliance on the underwater cables soars, a growing list of countries – and even companies – have the expertise to deploy unmanned vehicles to ocean depths to access them.