Today marks the 150th annual Peter Pan Cup -the annual Christmas Day race for swimmers braving the icy waters of theSerpentine in Hyde Park.
Around 70 participants will swim 100 yards starting from the south side of the lake. They'll be braving water temperatures of just six degrees celsius - and wetsuits are banned, with only normal swimming gear allowed.
Swimmers of all ages take part in the race each year on Christmas morning. The oldest participant this year is 74 year old Emmi Hunte from West Kensington, with the youngest swimmers just 11 years old.
The Serpentine Swimming club was founded in 1864, with the first Christmas Day race taking place that year. In 1903 legendary author JM Barrie donated a prize to the winner - which earned it the name the Peter Pan Cup. The prize has been give out every year since.
Because of the freezing temperatures, only club members can take part after they have practised swimming in the river for the months leading up to the race.
Anyone can go along and watch however - the race starts at 9am next to the Serpentine Cafe.