Beneath the waves of our seas and oceans lie 700,000 miles of cables, tasked with carrying the world’s internet and telephone traffic.

About the width of a garden hose, they lie draped across seabeds, linking countries and continents, handling around 99 per cent of global internet activity. Without them, this planet would seem a much bigger place.

Evidence of the 290-odd submarine cables that, if dredged up would encircle the globe 28 times round, is scarce, unless you know where to look.

Study the map below created by Esri UK, charting every single fibre-optic cable laid since their inception in 1988 - the first being the TAT-8; the previous seven were copper - and you will see that although they spend much of their existence under water, each must hit land at some point.

Take Porthcurno, a sliver of coast in view of the famous outdoor amphitheatre, the Minack Theatre. It was on this sandy beach in 1870 that some of the first under-water cables came ashore. The concrete cable hut, which managed those that arrived there, is today a listed building, while glimpses of cable can somestimes be caught on the beach.

The village is also home to the Telegraph Museum, where you can learn about the roots of modern communication.

The beach at Porthcurno Credit: Getty

Today more and more of the UK’s coastline welcomes transglobal cables, from Blackpool to Brighton, Dartmouth to Deeside. Douglas on the Isle of Man, too, is linked to the British mainland by cable.

As you can see from the map, some parts are better-positioned for cables than others. Widemouth Bay near Bude, for example, sees eight cables meet, connecting the UK with the US, west Africa and Canada, among others. The proximity of GCHQ Bude is no coincidence.

Widemouth Bay, near Bude, where a number of cables come ashore Credit: Getty

How long are the cables?

Some are short, such as the 81-mile CeltixConnect that joins Ireland to the UK, while others are tremendously long - take the 24,233-mile SeaMeWe-3, which has dozens of landing points around the world, including Goonhilly Downs in Cornwall.

Where can I see them?

On many of the beaches they come ashore, cables are sometimes visible by sand erosion, or where they leave the beach to higher ground. Careful not to trip over.

Work on a cable on La Seyne-sur-Mer in the south of France Credit: Getty

How are they laid?

How you might imagine. Boats traipse out to sea lowering the weighted cable behind, careful not to damage them.

The cables have some eight layers - including petroleum jelly, mylar tape and an aluminium water barrier - to protect them from everything that lurks in the depths. The optical fibers are at the centre. Prior to the Eighties, cables were hefty copper affairs

In a 2011 article detailing how the first transatlantic cable was lowered, Wired explained that the original line broke a number of times before a successful completion.

The laying of the first transatlantic cable Credit: Getty

“The boats met in the centre of the Atlantic on July 29, 1858, and attached the cables together,” Duncan Geere said.

“Crucially, there were no cable breaks, and the Niagara made it to Trinity Bay in Newfoundland on 4 August, and the Agamemnon arrived at Valentia Island off the west coast of Ireland on 5 August. Over the following days, the shore ends were landed on both sides using a team of horses, and tests were conducted.”

A section of cable laid across the River Medina in 1878 and believed to have been used by Alexander Graham Bell Credit: Getty

The first message was one of congratulations from Queen Victoria to President James Buchanan. However, signal quality deteriorated and the cable was destroyed only a month later when excessive voltage was put through it.

By the end of the 19th century a number of more reliable links - owned by the US, British, French and German - criss-crossed the Atlantic.

What’s the future?

The Marea cable, operational next year, will be the fastest ever to cross the Atlantic. Built by Microsoft and Facebook, the data cable will cross from Virginia Beach, Virginia, to Bilbao in Spain.

The 4,100-mile link will be capable of transmitting data at up to 160 terabits a second - the equivalent of streaming 71 million HD videos simultaneously.

Map created by mapping and spatial analytics company Esri UK