From the telegraph wires laid across the Atlantic in the 1860s to the fibre optic wires carrying digital data today, our oceans are criss-crossed with lines used for 98% of our communication (pdf). But when technology is superseded or a company ceases to trade, what happens to the cables and their copper, aluminium, steel and plastic? Some companies upgrade the cable to make it fit for purpose, others can reuse it (and its accompanying repeater devices, which help transmit signals). It can also be recycled into raw material for industry.