About 70 pilot whales which became separated from their pod and stranded near Farewell Spit, at the top of the South Island, have made it to deeper water.

Department of Conservation (DOC) spokeswoman Trish Grant told NZPA the high tide had enabled volunteers to refloat about 19 whales near Puponga, about 25 at the base of Farewell Spit on Triangle Flat, and about 25 whales 10km down the spit. A further three died.

It was the third time the whales, all from the same pod, had beached.

In a heartwarming reunion, the whales from all three groups had linked up in deeper water in Golden Bay.

"We were able to co-ordinate the release of the whales off the base of the spit just as the whales from Puponga arrived, so there was a moving moment when the whales swam straight towards the other members of their pod and they started milling around together.

"It was really pleasing because they're like a big family, they have strong bonds to each other and they want to be together, and also it's easier to manage them as a single group."

The third group found the rest of the pod about 2.30pm today, she said.

The whales had not been sighted since about 3pm, which was a good sign, but they were not in open ocean yet and the shallow waters at low tide meant there was still a real chance they could restrand.

Boats had been following the whales and trying to herd them in the right direction, while hundreds of volunteers on the shore were doing what they could to stop them getting too close to land by forming human barriers in shallow spots.

"They (the whales) are also getting increasingly tired and weakened. A lot of them have got cuts after coming into contact with rocks and shells and things like that and they've been exposed to lots of sun. It was also very distressing for them to have been stranded, so it's still touch and go at the moment," Ms Grant said.

One of the whales came perilously close to restranding but volunteers on the shore managed to deter it, she said.

Volunteers remained posted on the spit keeping an eye out for the mammals.

It was not known why whales stranded but theories included navigational mistakes, Ms Grant said.

"Farewell Spit is a bit of a trap. You need to veer right to get past it, and they didn't seem to know that.

"It's something that has occurred reasonably often in Golden Bay with pilot whales."

Pilot whales are about 4m-6m long. They are the most common species of whale seen in New Zealand waters.

Last month 24 pilot whales died after stranding in Parengarenga harbour, near Cape Reinga in the Far North.

In December 2009, more than 120 whales died in two separate beachings at Farewell Spit and Colville Bay, north of Coromandel.

In December 2006, rescuers managed to save the majority of 140 pilot whales stranded at Puponga Bay.

But just two weeks later, on New Year's Day 2007, 50 whales died after beaching at Farewell Spit.