'We have been to hell and back': Stranded sailors rescued off Sydney coast

A couple say they encountered waves the size of buildings, winds they couldn't stand in and "whiteness everywhere" as they awaited rescue on their broken yacht off the coast of Sydney.

Irishman Nick Dwyer and Frenchwoman Barbara Heftman arrived safely in Balmain on Wednesday night aboard a NSW Police rescue vessel with the "absolute heroes" who travelled more than 200 nautical miles in treacherous seas to save them.

"We have been to hell and back," Mr Dwyer said. "We owe them [the rescue teams] our lives."

They activated the yacht's emergency radio beacon three days later, on Tuesday afternoon, after their yacht "rolled" during a heavy swell and high winds.

“The sea is breaking, whiteness everywhere, a beautiful glory of terror facing you,” a clearly shaken Mr Dwyer recalled the horrifying experience.

"We encountered enormous seas, waves the size of buildings coming at you constantly, winds that you can't stand up in and seas breaking, whiteness everywhere."

The experienced sailors had been sailing from New Zealand to Australia in a 12-metre vessel as part of a 10-year circumnavigation of the globe when the yacht's rudder broke on Saturday.

The couple were rescued just in time as they struggled to remain above sea level on their sunken 12-metre vessel. Source: 7 News

Irishman Nick Dwyer and Frenchwoman Barbara Heftman said they owe their rescuers their lives. Source: 7 News

"Barbara and I were waiting after the boat turned upside down, holding each other, thinking for a split second that seemed to last for an eternity, 'is she going to turn upright?'" Mr Dwyer told reporters in Sydney.

Each time another wave hit, the couple wondered if the sea would ultimately claim their lives.

Nemesis set off in response to their emergency beacon on Tuesday night and reached the yacht - some 210 nautical miles northeast of Sydney - on Wednesday morning in six-metre swells and gale-force southerly winds.

Mr Dwyer said the yacht had been their home for the past 10 years and they weren't sure what they would do next.

"It was truly amazing, to think that somebody had come that far to save us," Mr Dwyer said.

The pair were transferred to the Nemesis by a container ship, the ANL Elanora, while their yacht was left to drift at sea.

Mr Dwyer said the yacht had been their home for the past 10 years and they weren't sure what they would do next.

"Our home's gone, we're alive, I expect to live a little bit longer and that'll be okay," he said.