James Carr, from Workington, will today begin a 4-day challenge in a bid to raise £10,000 for charity.
He's hoping to raise money for 2-year-old Emily Shutt, who's being treated for leukaemia both at home and at the Royal Victoria Infirmary in Newcastle.
Mr Carr, 37, has lost 4 stones in weight since September last year and the training and gym sessions have encouraged him to take on the challenge.
The event takes place over 4 days, beginning with a marathon from Workington to Whitehaven today.
The following two days will feature rowing and swimming challenges before finishing with a coast to coast cycle event in Newcastle on Tuesday 11th September.