Volunteer swimmers at Tooting Bec Lido helped fundraise £8,000 when they plunged into the pool’s winter waters at an event last month.
Around 150 people took part in the charity’s Icebreaker challenge on 26 January by paying £25 to jump into the cold water.
Further donations from non-participating members of the public more than doubled the final tally.
Director of fundraising Richard Lee said: “It’s amazing so many people were prepared to jump into a freezing lido to help us support homeless people.
“We couldn’t do what we do without such incredible supporters and the lengths people will go to is truly incredible.”
Last weekend’s Icebreaker event was the second fundraiser Crisis has staged in south west London this winter, after 70 people took the plunge at Brockwell Lido in December.
In total the challenge has raised £28,000 during the past two months, an amount the charity said will give more than 1,100 homeless people the counselling and support required to rebuild their lives.
Figures released by the Combined Homelessness and Information Network (CHAIN) on Thursday revealed 3,289 people slept rough in London between October-December 2018, marking a 25% increase from the same period in 2017.
Nationally more than 170,000 people are experiencing the worst forms of homelessness, including sleeping on streets and sofa-surfing with strangers, according to research from Heriot-Watt University.
Community and events executive, Rosie Birch, said: “People get bored of colleagues asking them to sponsor them for a 5km run.
“This event is something quirky and there’s not much preparation you need to do for it, you just need a swimming costume and a towel.”
Volunteers at last weekend’s event encouraged others to jump in before the Icebreaker season ends in four weeks.
Kelly Stanton said: “My body went into complete shock and I couldn’t wait to get out, but it was worth it.
“January can be a miserable month so it was good to do something different for charity.”
Fellow participant Lizzie Jones added: “These events bring people together and it’s a therapeutic thing to do.”
“It doesn’t take much for someone to become homeless,” Simon Ffoalkes warned.
Anyone who has been homeless in the last two years can receive free education, training and support at Crisis’s Skylight centre in Croydon, which is open all year round.
More information on the Icebreaker challenge is available on the Crisis website.
First time outdoor swimmers are also advised to check Crisis’s cold water tips before taking part.
Feature image credit: Hannah Maule-Ffinch.