An extensive network of underwater cables, called submarine communications cables, links up the continents and transmits Internet data across the globe.
You can browse an interactive map of these cables at the Submarine Cable Map.
The map depicts routes of 263 in-service and 22 planned undersea cables. Each country is colored according to how many international submarine cable system links are connected there. Capital cities and the location and direction of 44 cable vessels (as of December 6, 2013) are also provided.
All continents are currently linked except for Antarctica. The map includes a diagram highlighting the various parts of a submarine cable system, including a submarine cable cross section.
Importance of submarine cables
Submarine communication cables (submarine cables) are laid along the seabed to carry telecommunications signals between land based stations.
They remain more reliable than satellites and possess a much larger capacity, transmitting approximately 95 per cent of all international data between continents and islands.
Submarine cables are considered reliable because multiple paths are available for transmitting data in the event of a cable malfunction; they are also capable of transmitting terabits of information per second compared with often only megabits per second via satellite services.
Modern submarine cables use fibre optic technology and cost hundreds of millions of dollars to construct and lay, but they transmit the digital payloads for telephone, internet, and private data traffic to which consumers worldwide have become accustomed. [information source]