A search by Geraldton volunteer marine rescue was unable to find the man who was stranded 16km of Western Australian coast. Photograph: Geraldton Volunteer Marine Rescue Facebook

A scuba diver has survived eight hours in the Indian Ocean after becoming separated from his boat, leaving rescuers marvelling at his 16km epic swim to shore.

The 46-year-old had been diving with another man at African Reef off the Geraldton coast on Thursday when he resurfaced and couldn’t find their vessel, which had been cast adrift when the anchor rope broke.

The other man managed to find the boat and called Geraldton volunteer marine rescue group just after 7pm.

“We got the boat in the water straight away,” spokesman Ian Beard said.

The local maritime training college and three cray boats joined the search but the nighttime conditions and rough seas meant they went straight past the stranded diver.

He had a reflective strip on his buoyancy jacket, but it wasn’t enough to make him stand out.

“They’d gone past him, apparently, on a number of occasions,” Beard said.

“He didn’t have a torch or a strobe or any way of signalling.

“In the dark and in nasty, choppy conditions, it was like trying to find a needle in a haystack.”

In the early hours of the morning – around the time rescuers were heading back to refuel with plans to resume the search at first light – the diver spotted torch lights as his desperate family members scoured the shoreline. He used them to swim his way back to land.

They found him on the beach about an hour later around 3.20am.

“I can just imagine what a reunion it was,” Beard said. “It was a big swim.”

The man was taken to hospital for a check-up and would have been close to suffering hypothermia, which can be fatal, Beard said.

Rescuers were ecstatic, particularly given they’d suffered the recent blow of a kite boarder drowning after being dragged through the water face down.

Beard said it was the second most amazing tale of survival he’d encountered in eight years as a volunteer marine rescuer.

It was topped only by some men who were tipped out of their boat while pulling cray pots and managed to set off an obsolete personal locator beacon, which was picked up hours later by a customs aircraft that happened to be flying overhead.

Beard said the divers’ boat was too small for the conditions, had no operating radio and they also should have had personal locator beacons. They had an emergency position indicating radio beacon but that was on the boat, which wasn’t much use.

He strongly recommended people in boats use their radio to log on with the local sea rescue group as they set off.