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 not specific to the river habitat. The Thames contains both sea water and fresh water, thus providing support for seawater and freshwater fish. However, many populations of fish are at risk and are being killed in tens of thousands because of pollutants leaking into the river from human activities. Salmon, which inhabit both environments, have been reintroduced and a succession of fish ladders have been built into weirs to enable them to travel upstream. On 5 August 1993, the largest non-tidal salmon in recorded history was caught close to Boulters Lock in Maidenhead. The specimen weighed and measured in length.