Four-year-old Jaylen makes a splash for the first time

A Melbourne boy born with his intestines outside his body has celebrated his fourth birthday with his first ever swim.

Jaylen Cornish took the plunge like a duck to water with the help of his devoted mother Katie and a $600 'dry' wetsuit shipped to them by a generous donor.

When Jaylen was born with the rare condition the diagnosis was grim.

"The surgeon said to me look it's a lot worse than what we thought it was," Ms Cornish said.

"They said we're not sure whether he's going to survive the operation."

Although Jaylen pulled through, he now relies on two tubes to pump life-saving nutrients and medication into his system.

Since birth he has endured 22 operations at the Monash Children's Hospital and spent just six months outside the wards.

Ms Cornish is a sole parent and works tirelessly to keep his tiny body germ-free and dry to avoid infection.

"Every time we go past a pool or whatever he will start pointing and say 'mummy I want to go swimming, mummy water'," she said.

Young Jaylen's wish for his first ever swim has finally been granted in time for his fourth birthday.

The young fighter was fearless in the water, enjoying some splashes and even a solo paddle.

"He has got an opportunity in life to do things he has never been able to do before. Swimming is a big thing," Ms Cornish said.

"I think this is the best gift that anyone could ever ask for."