Rescuers frantically took to the sea after a 68-year-old scuba diver, John Leslie Brierley, went for a solo dive at the Yongala wreck dive site in Australia but failed to resurface.
"It's like looking for a needle in a haystack," Acting Inspector Graeme Patterson told reporters.
Rescuers started off with an air search and looked for him in a helicopter for 90 minutes, they were about to head back to base when they noticed something in the water.
Brierley was eventually spotted in the water after he spent more than 14 hours underwater — 50 km from where he had gone missing.
"There was a sense of urgency because we were heading back for fuel, but we wouldn't have been back for an hour," said Alan Griffiths, the air rescue officer who saved the man. "I said to him, 'G'day mate, do you want a lift?'"
Brierley was on his own without any personal locator beacon.
"He's gone by himself, which is a bit naughty," said Griffiths. "He jumped in the water from his boat and then realized the current was so strong and he simply couldn't get back."
"He was very, very lucky," Griffiths said. "He said to me, 'You need to buy a lottery ticket,' and I said, 'No, you need to buy a lottery ticket."
Paterson said it was extraordinary to find the diver alive.
“Every hour that somebody spends in the ocean, their chances diminish, so the fact that he’s been found in the first 24 hours is amazing,” he said.
Brierley was transported to the hospital for assessment. Speaking from his hospital bed, he said he was "euphoric" when he was finally spotted in the ocean about 25 km from his boat.
"The chopper crew were fantastic, the hospital staff have been fantastic, the police did a great [job]."