Volunteers and conservationists in New Zealand who endured frigid temperatures to help hundreds of beached pilot whales return to the water continue to have their work cut out for them.

A charity that helps protect marine mammals said Sunday that about 17 of the creatures were discovered stranded again near a roadside of South Island's Golden Bay after volunteers had spent Friday and Saturday trying to save 650 of them. Many of them were already dead, although about 240 whales refloated themselves.

"Our medics are attending to the 17 live whales," Project Jonah said on Facebook.

Nearly two dozen people were using buckets and cloths to help keep the beached whales wet, while a spotter plane was patrolling the area to see if there were any more whales heading inland toward the bay.

Pilot whales grow to about 25 feet and are common around New Zealand's waters.

The 17 whales came from a pod of 200 that were left stranded Saturday on Farewell Spit, a sand spit at the tip of the South Island, said Amanda Harvey, the Department of Conservation's biodiversity ranger.

Volunteers worked until late into the evening to help that pod return to the sea, with the humans having to jump out of the water when the high tide emerged, bringing the increased risk of stingrays.

"I was here first thing this morning and there was a small group of us," Kyle Mulinder, a volunteer with Project Jonah, told The Associated Press. "And essentially we went out and saw one of the biggest strandings I've ever seen."

Despite the new beachings, conservationists celebrated the successful refloating of about 180 whales, although they remained weary that they could strand themselves once again.

If the whales do rebeach themselves, Harvey said more volunteers will be needed.

Earlier, an initial group of 416 stranded whales were found early Friday, although many of them were dead.

A volunteer pours water on pilot whales at Farewell Spit on Saturday. MARTY MELVILLE / AFP - Getty Images

Department of Conservation Golden Bay Operations Manager Andrew Lamason said about 20 of the new group stranded Saturday were euthanized by conservation workers because they were in poor condition.

Lamason said about 100 surviving whales from the initial group on Friday were refloated, and dozens of volunteers had formed a human chain in the water to prevent them from beaching themselves again.

"I've never experienced death like this before," said volunteer Jonathan Jones. "You know, for such a majestic animal, it's really strange to see them doing this."

Experts have different theories as to why whales beach themselves, from chasing prey too far inshore to trying to protect a sick member of the group.

Farewell Spit has been described as a whale trap. It has a long protruding coastline and gently sloping beaches that make it difficult for whales to swim away once they get close. It has been the site of previous mass whale beachings.

Dead pilot whales line the shore at Farewell Spit, Saturday. MARTY MELVILLE / AFP - Getty Images

Officials will need to dispose of hundreds of carcasses soon.

Lamason said one option was to tether them to stakes in the shallow tidal waters and let them decompose. The problem with towing them out to sea or leaving them was that they could become gaseous and buoyant, and wind up floating into populated bays.

New Zealand has one of the highest rates of whale beachings in the world. Friday's beaching was the nation's third-biggest in history, the AP reported.

"So it's a very large one," said Rochelle Constantine, a marine biologist. "Logistically it's a massive undertaking."

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Volunteers in New Zealand Race to Save 17 Whales Stranded After 650 Beached - NBCNews.com