Organised by the RNLI, Splash Fest is taking over Battersea Park for the entire day on 7 August.
Five fun aqua challenges will be set over a 2.5k course, with names like the 'bubbly brook maze', a 'crazy canyon' and a 'slip-slide stream'.
And bubbles. Everyone loves bubbles.
There's also a more relaxed, chill-out zone where you'll be able to relax, play and grab a bite to eat.
The target age is 7-12 year olds, but we reckon there'll be plenty of family-friendly fun for everyone.
Book your tickets before 30 May, and you'll get a discount: £15 for adults and £7.50 for kids (up to 18). After 30 May, the standard ticket price is £22 for adults and £10 for children.
Wait, and a ticket on the day will cost £25 for adults and £12.50 for children. (Under 3s go free.)
Find out more and book on the website.