An area of the Serpentine, in Hyde Park, was opened to swimmers in 1930, although people have been swimming in the Serpentine for much longer and the
Serpentine Swimming Club was founded in 1864. The creation of a purpose built lido area was overseen by the MP
George Lansbury, hence it is often referred to as Lansbury's Lido.

Whilst the Swimming Club pride themselves on swimming in ice cold waters all year, and have famously been undertaking the Peter Pan Cup swim at 9am every year on Christmas Day for more than 100 years, the Lido is only open in the summer months and boasts a sunbathing area, a children's playground and changing rooms. With autumn fast approaching now is the time to take advantage.
Whilst information is limited, ***swimming costs £4 for adults and £1 for children and families of 2 adults and up to 4 kids can swim for £9- thanks mandm in comments*** and the lido is open usual daytime hours from roughly 10am to 5pm. Visit the website at
http://www.serpentinelido.com/ Picture from Geograph courtesy of Shaun Ferguson under Creative Commons