Answer: Sharks

Historically, undersea communication cables were incredibly thick, and thanks to their mass and the amount of steel cabling and insulation wrapped around them, largely impervious to damage. Modern communication cables, however, are much thinner since they are fiber optic instead of copper. Not only does this make them more susceptible to damage, but one particular problem arose shortly after the deployment of the first fiber optic cables: shark attacks.

Why would a shark attack a cable sitting on the bottom of the ocean? Not only do the cables carry light-based data signals, they also carry a companion electrical signal to power the repeaters built into them. The electrical signals attracted sharks, who interpreted the signal as an indication the cables were alive, and sharks would damage the cables in an attempt to eat them. Now, fiber optic cables are laid with a special undersea plow that creates a furrow for the cables and then buries them—safely entombed in the sea bed, the cables are protected from the nips of curious sharks.