In 1873, Webb was serving as captain of the steamship Emerald when he read an account of the failed attempt by J. B. Johnson to swim the English Channel. He became inspired to try himself, and left his job to begin training, first at Lambeth Baths, then in the cold waters of the Thames, the English Channel and Hollingworth Lake.
His early training was backed by Fred Beckwith who was the "Professor" at Lambeth Baths. Beckwith organised a spectacle by showing Webb swimming miles in the River Thames. Webb completed ‘nearly six miles’, but the poor public interest meant that Beckwith lost money. As a result Webb took another manager.
On 12 August 1875, he made his first cross-Channel swimming attempt, but strong winds and poor sea conditions forced him to abandon the swim. On 24 August, he began a second swim by diving in from the Admiralty Pier at Dover. Backed by three escort boats and smeared in porpoise oil, he set off into the ebb tide at a steady breaststroke. Despite stings from jellyfish and strong currents off Cap Gris Nez which prevented him from reaching the shore for five hours, finally, after 21 hours and 45 minutes, he landed near Calais—the first successful cross-channel swim. His zig-zag course across the Channel was over 39 miles (64 km) long.
https://en.wikipedia.org/wiki/Matthew_Webb