For some of New Zealand's beached whales, a happy return to the sea

Overnight on Sunday, more than 200 stranded whales were able to refloat themselves and swim off with another 17 whales saved by volunteers at high tide.

This comes as the latest piece of good news after a challenging weekend for whales in New Zealand.

On Friday morning, locals near Golden Bay on the tip of New Zealand’s South Island discovered a group of about 400 whales beached on the area’s Farewell Spit. A department staffer first spotted them Thursday night and by the time they were discovered on land the next morning nearly 275 were already dead.

Within hours, locals and tourists came out in enormous numbers to help employees of the Department of Conservation keep the mammals cool and comfortable during efforts to refloat them.

"There's like two to three hundred carloads of people who have come to help, maybe three to four hundred people," department of conservation community ranger Kath Inwood told CNN on Friday.

By mid-morning, the rescuers had managed to refloat more than 100 whales, only about 50 of whom returned to sea. According to Inwood, just five hours later another 80 to 90 that were freed had become re-stranded in the same place as before.

Rescue attempts halted overnight over safety concerns for the volunteers, as the large, stressed animals could become dangerous to those trying to help them.

Volunteers returned Saturday and successfully refloated the surviving whales, only to learn hours later that another mass stranding had occurred. 

According to a Department of Conservation spokesperson, the second mass stranding involved a different pod, because all of the previous re-floated whales had been tagged upon their release and none of the second group had any tags, reported ABC News.

Farewell Spit on New Zealand’s South Island poses a particularly hazardous challenge for local marine mammals as every year pilot whales and dolphins become stranded on the thin stretch of sand that extends in an arc over the top of the Island’s Golden Bay.

"There's a lot of theories out there as to why it happens, but at the end of the day I think there's four or five hotspots where they strand [in New Zealand], and the one thing they all have in common is shallow water,” Gary Riordan, a local who runs a beachside camp ground nearby, reported the BBC.

According to Dr. Rochelle Constantine, a marine biologist at the University of Auckland, the shallow water proposes a challenge to the pilot whales, which despite their name are actually a species of dolphin.

“They can echo-locate, but it's [a problem with] the signal that they get bounced back.” Dr. Constantine told the BBC. “It's a combination of this gentle gradient and the soft sand. They probably aren't detecting that they are swimming into more and more shallow water.”

Once the pod realizes they are too far in, the ebb tide has begun and the animals are left stranded on the exposed sand.

Deep-water species with higher than ordinarily developed social structures are most at risk, according to Project Jonah. “One of the most common patterns with mass strandings is that one or two whales will initially strand. These animals will send out distress signals and members from their pod may attempt to help or mill slightly offshore. A receding tide will then catch these animals out and soon the whole pod will become stranded.”

When rescuers arrived to aid the helpless animals, they found a dismal sight. 

“It was just red and pink skies and just whales as far as you could see,” Cheree Morrison, a magazine editor, told The Washington Post. “It was really haunting.”

While hundreds of the whales died, Sunday morning finally saw some good news for the region, when the would-be rescuers discovered that overnight some 200 stranded whales had been able to refloat themselves and swim away.

At high tide, rescue workers saved an additional 17 whales.