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 The eel is particularly associated with the Thames and there were formerly many eel traps. Freshwater fish of the Thames and its tributaries include brown trout, chub, dace, roach, barbel, perch, pike, bleak and flounder. Colonies of short-snouted seahorses have also recently been discovered in the river. The Thames is also host to some invasive crustaceans, including the signal crayfish and the Chinese mitten crab. Aquatic mammals are also known to inhabit the Thames. The population of grey and harbour seals numbers up to 700 in the Thames Estuary. These animals have been sighted as far upriver as Richmond. Bottlenose