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 in the Thames estuary occurs in the central London area between Vauxhall Bridge and Woolwich. The majority of sediment cores show a clear decrease in Hg concentrations close to the surface which is attributed to an overall reduction in polluting activities as well as improved effectiveness of recent environmental legalisation and river management (e.g. Oslo-Paris convention). Evaluation of select of lipid compounds in the Thames estuary, known as glycerol dialkyl glycerol tetraethers (GDGTs) has revealed enhanced concentrations of isoprenoid GDGT compounds (crenarchaeol) around East London. This suggests that London's pollution affects the spatial distribution of natural carbon in the river