The Serpentine (also known as the Serpentine River) is a 40-acre (16.2 ha) recreational lake in Hyde Park, created in 1730 at the behest of Queen Caroline. Although it is common to refer to the entire body of water as The Serpentine, strictly the name refers only to the eastern half of the lake. Serpentine Bridge, which marks the boundary between Hyde Park and Kensington Gardens, also marks The Serpentine's western boundary; the long and narrow western half of the lake is known as The Long Water. The Serpentine is commonly thought to take its name from its snakelike, curving shape, although it only has one bend. The name is more correctly derived from the colour of the water and was named by Queen Caroline due to this observation.
Originally fed by the River Westbourne in the 1730s, the lake's water was then pumped from the Thames in the 1830s. The water is now pumped from three boreholes within Hyde Park, the most recent being installed in May 2012 as part of the 2011-2012 restoration of the Lake. The Serpentine provided a focal point for The Great Exhibition of 1851, and more recently was a venue for the men's and women's triathlon and marathon swimming events in the London 2012 Olympics. Since 1864 the Serpentine Swimming Club has organised a 100-yard race every Christmas morning for the Peter Pan Cup, inaugurated by J. M. Barrie, the creator of the fictional character Peter Pan.