River Thames to the strong current of the river, but also other river users. Organised swimming events take place at various points generally upstream of Hampton Court, including Windsor, Marlow and Henley. In 2011 comedian David Walliams swam the from Lechlade to Westminster Bridge and raised over £1 million for charity. In non-tidal stretches swimming was, and still is, a leisure and fitness activity among experienced swimmers where safe, deeper outer channels are used in times of low stream. A Thames meander is a long-distance journey over all or part of the Thames by running, swimming or using any of the above
River Thames Mudlarks scavenged in the river mud for a meagre living. In the 19th century the quality of water in Thames deteriorated further. The dumping of raw sewage into the Thames was formerly only common in the City of London, making its tideway a harbour for many harmful bacteria. Gas manufactories were built alongside the river, and their by-products leaked into the water, including spent lime, ammonia, cyanide, and carbolic acid. The river had an unnaturally warm temperature caused by chemical reactions in the water, which also removed the water's oxygen. Four serious cholera outbreaks killed tens of thousands of people