A 71-year-old grandfather has set himself a challenge to swim 100km (62 miles) in open water in one year to raise money for Brain Tumour Research.
Alan Holmes, from Bedlington, Northumberland, will complete about 400-500m per swim in the North Sea at Cullercoats Bay throughout 2021.
He is fundraising for the charity after his 18-year-old grandson was diagnosed with a second tumour in June.
Mr Holmes said swimming was "nothing compared to what he's going through".
Matthew Pullan, from Bury in Greater Manchester, was diagnosed with an Ependymoma when he was three years old.
The tumour was successfully operated on and he recovered well.
But in June doctors found a new tumour and he underwent surgery to remove it.
Mr Holmes, said: "He has been told his prognosis is 'poor' but he is determined to live life to the full and not to be defined by his cancer.
"He is currently going through chemotherapy, while studying from home and blogging about his diagnosis and treatment. I am so proud of him."
Mr Holmes is aiming to swim five times a week during daylight hours, wearing a wetsuit, thermal hat, gloves and footwear.
"I hate the cold water and so the first time I went in I really wasn't sure I wanted to do it. Prior to that I wouldn't even dip my feet in the water.
"I thought about why I was doing it and that motivated me to carry on.
"This is a major endeavour for me but it pales into insignificance compared with the challenge Matthew faces," he added.
Matthew said: "I'm very impressed by my grandpa, giving up his time to try and find a cure for something that I've been told will eventually kill me.
"I'm amazed by the challenge; he's a man in his seventies and he's swimming in cold, dangerous waters. I certainly couldn't do it.
"I love him so much. What a great person to be able to look up to."