The nightmares are gradually fading for two shipwreck survivors cast adrift in the South China Sea without food or water for 11 days.

Aussie Mark Smith, 49, and Kiwi Steve Freeman, 30, had seconds to leap into a six-man liferaft when the yacht they were delivering to Australia sank in heavy seas off the coast of Hong Kong late last year.

They drifted with no food or water for 11 days, drinking their own urine and agreeing if one died, the other would eat him.

"We shook hands on eating each other. I said 'If I'm dead, you're in mate'," said Mr Smith, an experienced fisherman and seaman.

The pair have been reunited for the first time since their ordeal to help promote the "G'Day NZ" Australian tourism campaign designed to capitalise on the "spirit of mateship" between the two countries.

"I think it did help us through, that [Australians and New Zealanders] are similar," Mr Freeman said.

The two are guests of honour at a gala dinner being held in Auckland tonight as part of the ad campaign.

Their misadventure began on December 5 when food and water in the liferaft went overboard in heavy seas. Each tried to keep the other going as they drifted day after day, the liferaft constantly overturned by huge waves.

Mr Freeman's physical strength helped get the raft upright each time it overturned, and Mr Smith would try to lift his mate's spirits when he became discouraged.

Mr Smith imagined in gruesome detail what he would do if Mr Freeman died.

"I knew how I would do it. A small slit in his neck and I'd get about five pints of warm blood," he said.

On the seventh day it rained, giving the men a few more days' survival, and it rained just enough over the next few days to help keep them alive.

Finally the raft was blown near an island off the coast of Vietnam, but the men were separated in breaking waves and Mr Smith was pounded by the sea. He almost gave up.

"I thought to myself, 'just take a breath mate, one swallow and it'll all be over'," he said.

But he kept his head above water until villagers rowed out to the rescue. The men's story made headlines round the world.

Mr Freeman said the adventure seemed "years ago".

He has returned to his Nelson home temporarily before once again heading to Australia to work as a fisherman.

Mr Smith has been working on a project to sink a dive wreck off the New South Wales coast.

"I've had a few nightmares but they are gradually fading and it's been brilliant catching up with Steve. With his strength and my brains, we made it through," he joked.