Hundreds of people in New Zealand worked together to successfully "refloat" 40 long-finned pilot whales that stranded on a remote beach, meaning they returned the animals to open water, The Associated Press (AP) reported.

The whales did not swim out into the deeper ocean, however, so some conservationists are worried that the animals may beach themselves a second time.

The 40 whales initially stranded Monday morning (Feb. 22) on Farewell Spit, a beach on South Island, along with nine other whales that died during the stranding, according to the AP. Conservation rangers from the New Zealand government worked with locals and the marine rescue group Project Jonah to tend to the surviving whales, pouring buckets of water over their skin and ensuring their fins weren't crushed beneath their beached bodies.

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High tide arrived in the evening, providing enough water for volunteers to refloat the whales, Louisa Hawkes, a Project Jonah spokesperson, told the AP. To refloat relatively small whales like long-finned pilots (Globicephala melas), which are members of the dolphin family, people typically use waterproof tarps to gently move the animals into open water and allow them time to reorient before swimming away, according to Particle, an Australian science publication.

In general, the whales can grow to be about 19 to 25 feet (5.7-7.6 meters) long and weigh between 2,900 and 5,000 pounds (1,315-2,267 kilograms) each, according to the National Oceanic and Atmospheric Administration (NOAA).They are not considered endangered, but scientists do not have enough data to precisely determine the long-finned pilot whale’s conservation status, according to Oceana.

The volunteers didn't note if they used tarps in this rescue, but because the whales on Farewell Spit were spread out along the beach, the crew first herded the animals back into a pod, the AP reported. Roughly 200 people then formed a barrier at the shoreline and guided the pod into deeper water; once the whales got deep enough, boats began patrolling the shore to block the whales from returning.

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But in the end, the whales didn't swim away into the ocean, so there's still fear that they may strand again, Hawkes told the AP. "Everyone is very hopeful but also very realistic," she said.

In New Zealand, long-finned pilot whales account for the majority of mass strandings, where two or more whales strand at one time, according to New Zealand's Department of Conservation. Sometimes, hundreds of whales can beach themselves at one time. Four years ago, for example, two mass strandings left 350 long-finned pilot whales dead on Farewell Spit, while whale rescue groups managed to refloat about 300 others, according to the AP.

Scientists still aren't sure why mass strandings occur. But whales' echolocation may not work well near the shoreline, so they might become disoriented and unable to find their way back to open water, Live Science previously reported. It's also possible that, once one whale strands, others in the pod follow close behind to help and end up beaching themselves.

Originally published on Live Science.