Optical Fibre at the bottom of the sea
What about it?
Undersea or "submarine" fiber optical cable widely for intercontinental and island communication about ten years ago, but the "repeater stations" required so much maintenance that they have mostly been abandoned. Some of the original companies that laid the cable went bankrupt. Engineers are now working on a new generation of better undersea fiber optic cables, using improved low-loss materials. See
http://www.technologyreview.com/Nanotech/13185/