Click here for all Olympic highlights and let the Games never end: go.olympic.org/watch
Full highlights from the Men's 4 x 200m Freestyle Relay Final in which Michael Phelps win's his record breaking 19th Olympic Medal as the USA secure Gold at the Aquatics Centre in London.
Subscribe to the official Olympic channel here: bit.ly/1dn6AV5
Swimming has featured on the programme of all editions of the Games since 1896. The very first Olympic events were freestyle (crawl) or breaststroke. Backstroke was added in 1904.
In the 1940s, breaststrokers discovered that they could go faster by bringing both arms forward over their heads. This practice was immediately forbidden in breaststroke, but gave birth to butterfly, whose first official appearance was at the 1956 Games in Melbourne. This style is now one of the four strokes used in competition.
Women's swimming became Olympic in 1912 at the Stockholm Games. Since then, it has been part of every edition of the Games. The men's and women's programmes are almost identical, as they contain the same number of events, with only one difference: the freestyle distance is 800 metres for women and 1,500 metres for men.
Find more about Swimming at www.olympic.org/swimming