Oliver Hill is taking part in a one kilometre swim to raise money for the hospital that have been looking after him since he was a toddler.
His mum, Sarah, said that he was diagnosed with a partial-collapsed lung in 2020, at the age of three, and has been under the respiratory team with Southampton General Hospital ever since.
Oliver will complete the swim on Saturday, March 28, but has already smashed his fundraising target of £1,000.
He was inspired to take up the challenge by his older sister Sophia, 11, who has completed charity swims in the past, including for Southampton hospital.
Sarah said: “Oliver wanted to do it because of his sister, and to raise money for all of the work the hospital has been doing.
She said the challenge, which involves swimming 40 lengths of the swimming pool, will be difficult for Oliver.
Sarah added: “It will be quite a challenge because he still gets tired after lessons.
“It’s amazing he’s doing this, he’s worked so hard at it, doing extra sessions on top of his normal swimming lessons.
“Seeing him develop and become more confident has been an achievement.”
Oliver said he is looking forward to taking the challenge on.
He said: “I feel really good, really brilliant about this.
“When I’m done I’ll probably be very tired but I’m going to be super proud.”
Oliver will complete his swim with Learn to Swim Southampton, which is part of City of Southampton Swimming Club.
Jenny Murphy, from Learn to Swim, said: “Watching Oliver’s confidence grow in his swimming over the past 18 months has been fantastic.
“We are proud of Oliver for his commitment and dedication towards his training to achieve this.”
A spokesperson for Southampton Hospitals Charity said: “Oliver is an inspiration; he has endured many years of treatment and appointments and his desire to give something back to say thank you for the care he’s received is wonderful.
“We’ve been following Oliver’s journey as he prepares for his challenge this weekend and we wish Oliver lots of luck.”