A couple stranded at sea on their yacht have given tearful accounts of being knocked unconscious and trying to stay strong while waves crashed over them.

Aucklander Tania Davies, 43, and her partner Australian-based Briton Steve Jones, spent two nights on board their damaged yacht before being rescued by a Chinese cargo ship.

Bad weather caused their yacht, Windago, to roll 700 kilometres southwest of Tonga.

The couple finally arrived in Auckland yesterday on the navy frigate HMNZS Otago.

Their $250,000 yacht was not insured.

"The waves were well over our mast," Davies said, recounting the ordeal. "Cupboards came off, doors came off.

"We heard winds, howling noises. We can't even explain the noises, can we? We just did what we could to stay alive.

"We got slammed but we didn't realise because we'd been knocked unconscious and had memory lapses."

The cargo ship MV Chengtu appeared "like a castle on the sea", such was their relief at being rescued,  Davies said. "It was such a sight."

Video footage of the pair being hauled on board the ship by crew using an underarm sling has been captured by Fairfax Media.

The pair were still visibly shaken by what happened.

"We knuckled down and stayed strong," Davies said. "We endured a day in good spirits and kept our humour up because that's a vital ingredient to get through something like this."

Jones suffered a back injury which was treated by medical crew and the pair were nursing bumps and lacerations.

They were relieved to be back on dry land. "Steve consumed four cups of coffee in six minutes, it had been a long time between hot drinks," Davies said.

She said it would be a while before they ventured out on a yacht again. Jones joked he planned to live on a farm with no sea view.

- © Fairfax NZ News