Not knowing exactly how long he had left, he — along with his partner Michelle Edgar and five-year-old daughter Amelie — decided to make some family memories that would last forever.
Ms Edgar researched dolphin swimming experiences in the hope that she could take the family on a holiday to swim with dolphins together, starting with Australian locations because, with so many pre-existing health conditions and five hospital admissions already this year, Mr Turner couldn't qualify for travel insurance.
But Aussie operators refused to allow Amelie to swim with dolphins as she was not big enough — she was born premature at 27 weeks, weighing just 606 grams and now is small for her age, being the size of an average two-year-old.
Fearing they would never be able to fulfil their dream, the family took a big risk and decided to travel to Singapore for just five days without health insurance.
"It was most definitely, an incredible experience that will be remembered for the rest of their lives," a close friend of the family wrote on a GoFundMe page to raise funds for the dying dad.
However, during the holiday, the unfortunate father fell again and badly injured his knee.
"His already compromised system now had to work even harder to repair the damage," the family friend wrote.
"To continue with their holiday, Duncan was now confined to a wheelchair and in was in serious pain. It was on the way home that things really took a turn for the worse."
The family were just 30 minutes from their transit destination of Bali when Mr Edgar took a severe turn and airline staff insisted he would not be fit to board their final leg flight to Perth. He was taken by ambulance to a Bali emergency department and admitted to hospital for lifesaving blood transfusions.
In just a few days the family has racked up hospital bills and other costs totalling around $10,000. Their credit card is maxed out and they are unable to get consular assistance.
The family has no idea when doctors will clear him to fly home with Jetstar, and the bills are now stacking up, with a room at the Bali hospital costing $580 per night.
The desperate father has checked out of the hospital after several days due to the cost, but needs to go back for more treatment and could be re-admitted.
The family has created a GoFundMe page to raise the cash they need to get Mr Edgar home and it has brought in over $15,000 so far.
Ms Edgar said she realises the couple took the risk of travelling without insurance cover for Mr Turner.
"It was Duncan's wish," she told Fairfax.
"He wanted Amelie to have these special memories. We decided to go. We thought it would be fine."