An exhausted swimmer and her boyfriend have narrowly escaped drowning after being rescued by the support crew of the six lifeguards circumnavigating the country in two small rescue boats.

The lifeguards said it was an absolute stroke of luck the support crew was at the remote Oruaiti Beach on the East Cape yesterday, waiting for the two inflatable rescue boats to put ashore and restock.

The woman in her 20s had been caught in a strong rip and was 60m offshore when she began going under. Her boyfriend could no longer hold her up. They were both in serious danger of drowning, said team spokeswoman, Emma Darwen.

She said the team safety manager, who had fins only and no rescue tube, retrieved the woman with the assistance of rescue boat driver, Ash Matuschka when the boyfriend raised the alarm after making it shore.

"Had he stayed out in the water he probably would have gone down with her," Ms Darwen said.

She said the support crew wase meant to have landed at another beach but they changed their plans at the last minute and called in at the remote and unpatrolled Oruaiti Beach.

"They (the support crew) had parked up minutes earlier and then it all unfolded."

She said the woman was exhausted and shaken.

"She was very, very grateful."

The two rescue boats are doing a 5200km circumnavigation of New Zealand to commemorate 100 years of lifesaving in New Zealand and pay tribute to the lifeguards who have patrolled the beaches for the last century.

They were due to land at Mt Maunganui today and when they finish the journey in Auckland on Monday they will have made history by becoming the first people to circumnavigate the country, including Stewart Island, in an inflatable boat less then four metres long.

The trip had largely been without incident until Thursday when one of the boats hit a submerged piece of wood and a nail ripped open the left hull.

It was towed ashore and replaced with the spare hull carried by the support crew. They were also delayed for three hours at Birdlings Flat last week as they were about to round Banks Peninsula when a rogue wave rolled one of the boats.