SYDNEY (AFP) - Rescuers on Monday (Nov 7) hailed finding "a needle in a haystack" after plucking to safety a diver who had drifted more than 30 nautical miles from his boat and survived a night in Australian waters.

The 68-year-old failed to return from a solo dive on Sunday (Nov 6) at the Yongala wreck on the Great Barrier Reef - renowned as one of the best dive sites in the world - with the alarm raised by a friend.

A sea and air search was launched with his boat found during the evening, but no sign of the missing man.

He was spotted by a helicopter some 17 hours later after drifting more than 30 nautical miles in strong currents.

"It's a huge task for rescuers to search a grid pattern of the ocean and today's massive search area was calculated according to tides and currents," said RAC Queensland Rescue, which found the man. "Our crew will tell you trying to find a human in the ocean is similar to finding a needle in a haystack."

Mr Alan Griffiths was on the helicopter that found the diver and was winched down to get him. "I said to him, 'G'day mate, do you want a lift?'" he told the Australian Broadcasting Corporation.

"He said to me, 'You should buy a lottery ticket', I was like, 'No mate, you need to buy a lottery ticket.'"

The unnamed man was taken to hospital for assessment.

Police inspector Graeme Paterson said it was remarkable to find him 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.

The passenger ship SS Yongala sank off Cape Bowling Green in Queensland in 1911 after steaming into a cyclone, with all 122 on board killed.

It was found in 1958 and has become a major tourist attraction, with thousands of divers visiting every year.