BBC Breakfast presenters Naga Munchetty and Charlie Stayt chatted with guest Adam Ball on Saturday, who had been told he had "30 years to live".
Naga revealed at the start of the programme: "Given 30 years to live after being diagnosed with cystic fibrosis, how Adam Ball is defining predictions and celebrating his birthday by swimming the length of the Lake District's largest lakes."
Just before connecting with Adam via video link, Naga explained: "The time now is 20 minutes past six. Now, Adam Ball was just six weeks old when he was diagnosed with cystic fibrosis, a life-threatening condition affecting his ability to breathe.
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"Now, despite giving a life expectancy of 30, he's celebrating that milestone birthday by swimming the entire length of 13 of the Lake District's lakes."
Charlie added: "We spoke to him in May when he was halfway through that challenge. But today, he will complete the final swim, which is his toughest yet, seven and a half hours across Windermere," reports Bristol Live.
"And we can speak to him now he's in Ambleside. Very good morning to you. You have a challenge ahead of you today."
Adam nodded as he appeared on screen, prompting Naga to ask, "How are you feeling about it?"
"I am feeling good but nervous with it being the biggest one, but ready to go," Adam responded. "Ready to get into it."
Focusing on Adam's condition, Charlie remarked, "It is an extraordinary thing you're taking on and your whole life, effectively, you have defied what people say was to be expected of you, even right from your earliest days.
"Yeah, absolutely. I mean, you know, I think growing up with a sort of life-limiting condition, you do get a new perspective on things.
"And, you know, things haven't always been easy by any means, but I've always been grateful, in the sense of, despite having this illness, I've had very supportive people around me that able me to do sort of wonderful things and still live a good life and sort of push my limits.
"And I think certainly this challenge is a milestone there, and to raise awareness and inspire others, in the year in which, once upon a time, would have been, you know, sort of my limit, really."

He continued, "So, yeah, so it feels amazing to be able to sit here a day and know that we're taking on this challenge."
Naga then questioned Adam about the physical effects of cystic fibrosis and how it affects his swimming abilities. He explained, "So cystic fibrosis is very much individual to the person. It's quite rare, so it only affects around 11,000 people in the UK. For me personally, as you mentioned, it affects my lungs and my digestive system, so it creates a sort of thick, sticky mucus around the body, which, within the lungs, it clogs the airways, making it difficult to breathe, and within the digestive system, it makes it difficult to absorb food.
"So it kind of creates a bit of a vicious circle, in the sense of it being difficult to breathe, you tire out more, and then not being able to get the food, you kind of don't replenish the energy.
"So doing physical things can be quite challenging, but with a lot of the medication and treatments there, it has made it, in more recent years, a lot more able to do things."
BBC Breakfast airs daily at 6am on BBC One.
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