Lucy Chatting took on the challenge as part of her family's continued drive to support Birmingham Children's Hospital which cared for her son, Carter, 9, who has battled the disease.
The charity she and husband Matthew set up - Carter the Brave - has funded equipment to help make children's stay during treatment more bearable and it is funding a research project to improve the treatment of leukaemia in the young.
The project, Starve Leukaemia, will receive £7,600 while Round Table Children's Wishes will receive at least £400.
Lucy swam 500 lengths of the 20 metre pool at David Lloyd Leisure in Lichfield last Friday (October 8) cheered on by family and friends.
"I went really fast during the first 3 kilometres but then I pulled muscle in my right calf," said Lucy, 49.
"I had to have a massage in the pool and the last 100 lengths were hard going.
"I still managed to do it in less than 3 hours, 51 minutes."
There was a tombola and stalls selling prosecco and beer at the event which raised £700 - £7,300 was generated through sponsorship.
Lucy wishes to thank everyone who sponsored her.
Lucy would also like to thank the following people for their support, Neal McCathie who swam alongside her for 7.5 kilometres helping her pace the swim,
fellow swimmers, Radhika McCathie, Sunita Lally, Kirsty Mott, Claire Barber and Emily Hiskins, and the little swimmers who joined in; Lyra Robinson, Charlotte Morten, Abby MCathie, Isabelle Hiskins, Belle Collett and Monica Chatting.
"A massive thanks to Sarah Stokes, Radhika McCathie, Claire Barber, Sunita Lally, Nick Kaey and Harry Lally who did a totally awesome job running the stands," said Lucy.
"And enormous thanks to David Lloyd Leisure, Lichfield for hosting and Andy Lightbown for the planning too."
For more information visit Carter the Brave on Facebook.