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 sewage on the riverbanks, and decrease the water quality of the river. To prevent the release of raw sewage and rainwater into the river, the Thames Tideway Scheme is currently under construction at a cost of £4.2 billion. This project will collect sewage before it overflows, before channeling it down a 25 km (15 mi) tunnel underneath the tidal Thames, so it can be treated at Beckton Sewage Treatment Works. The result of the project will be reduction of sewage discharges into the river by 90%, dramatically increasing water quality. Mercury (Hg) is an environmentally persistent heavy metal which at