Two men are completing seven triathlons in one week to raise money for youth projects in Lincoln.
Dan Hargreaves and Stuart King say the cash will go to the city's most deprived areas to keep kids off the streets during the summer holidays.
The Olympic-length challenges are being completed over seven days across the UK and Ireland.
Each task requires the team to swim 1.5km before riding a bike for 40km and then taking on a 10km run.
The duo are putting themselves through the ordeal as part of their work for the Lincoln charity Acts Trust, which organises the Energize Holiday Schemes.
After setting off for Scotland on Monday, June 18, they have already visited Northern Ireland and the Republic of Ireland.
The final triathlons are taking place in Wales on Friday, then Glossop in Derbyshire on Saturday and at Yarborough Leisure Centre on Sunday.
Around 50 friends, family members and colleagues will join the challengers on their final task.
Individuals and teams of three people are also invited to take part.
Mr Hargreaves, 35, of Newland Street West in Lincoln, said the venture would be among the most difficult he has ever undertaken.
"I like a challenge – it gets the best out of people," he said before leaving for Scotland.
"I think we're going to be sweating blood and taking plenty of ice baths afterwards but it's going to be fun. I'm really looking forward to it."
The two men set up their own courses in and around leisure centres at each of the locations.
Each triathlon will take them around five and half hours to finish. The last event will coincide with a summer fair at Yarborough Leisure Centre.
It will include a barbecue, bouncy castle, face painting and other activities between 3pm and 6pm. Around £4,000 was already raised before the team set off, getting them closer to their £7,000 target.
The money will go towards sport sessions, fun days, dance classes and days out for people aged 11 to 18.
Mr Hargreaves said the Energise programme was important in keeping youngsters active.
"Young people have got so much potential but they get a lot of bad press," he said.
"We want to give them something positive to do in the holidays and make sure they don't get up to any mischief."
The Acts Trust was founded by the New Life Church in 2007. To make a donation, call 01522 626697. Alternatively, pick up a brochure from the New Life centre in Newland, Lincoln.