Olympic medal-winning swimmers Becky Adlington and Michael Jamieson battled their way to a Guinness World Record 100 x 100m swimming relay title to raise tens of thousands of pounds for cancer research.
The pair were joined by fellow Olympians Fran Halsall and Karen Pickering to tally up a new record of 1 hour 29 minutes and 3 seconds in Sheffield.
They destroyed the previous record of 1 hour 37 minutes and 53 seconds and endured the slog to raise more than £20,000 for blood cancer charity Leukaemia & Lymphoma Research.
The event was organised by Great Britain and Sheffield swimmer Lewis Coleman after his mother was diagnosed with acute lymphoblastic leukaemia in June 2012.
She has since been through chemotherapy, a clinical drugs trial and a bone marrow transplant.
Adlington, a double Olympic gold medallist, said she was buoyed on to beat the record to give Coleman a helping hand.
London 2012 Olympic silver medallist Jamieson said: "I'm in awe of everything that's happened today. There's a huge amount of money being raised.
"Lewis is a friend and for him to pull this off is unbelievable. The atmosphere's brilliant, everyone's enjoying it, though the swimmers were really nervous."