More than 170 whales beached themselves Friday in New Zealand’s Golden Bay, and some 25 have already died in the shallow waters as volunteers race to save them. The pod of pilot whales has fallen victim to a sandbar called Farewell Spit – one known as a death trap for whales. Beaching incidents are not infrequent in Farewell Spit (last January saw two in the span of just a week), but this is the largest in over a decade.

An organization called Project Jonah has trained around 140 volunteers in the area to save beached whales, and many of them are working diligently to “refloat” the surviving whales. About half of the pod seem to have moved to deeper waters without help, but the rest need aid before they die of dehydration or suffer from severe sunburn.

It’s not easy to refloat a beached whale: Pilot whales, which are members of the dolphin species and quite common in New Zealand, can weigh up to 3 tons. Volunteers will have to rely on the high tide’s deeper waters to push them back into safety. Every time the tide goes out, volunteers are left powerless to help the whales until the next day.

Even if the volunteers successfully push most of the pod out to sea, the pilot whales might turn around and come back.