The English Channel is the busiest waterway in the world.Ferries steam back and forth, trains thunder through the tunnel.The narrow sea has been crucial to our development and prosperity.It helps define our notion of Englishness, as an island people, a nation of seafarers.It is also our nearest, dearest playground where people have sought sun, sin and bracing breezes.Tom Fort takes us on a fascinating, discursive journey from east to west, to find out what this stretch of water means to us and what is so special about the English seaside, that edge between land and seawater.He dips his toe into Sandgate's waters, takes the air in Hastings and Bexhill, chews whelks in Brighton, builds a sandcastle in Sandbanks, sunbathes in sunny Sidmouth, catches prawns off the slipway at Salcombe and hunts a shark off Looe.Stories of smugglers and shipwreck robbers, of beachcombers and samphire gatherers, gold diggers and fossil hunters abound.