Twenty pilot whales died on a New Zealand beach after stranding but holiday-makers and conservation workers Sunday managed to coax 43 others back out to sea.

Rescuers monitored the survivors as night fell as they swam away from Colville Beach on North Island's Coromandel peninsula, hoping they would not turn back to the beach.

Department of Conservation workers and hundreds of volunteers helped refloat the 43 whales at high tide. The volunteers covered the stranded mammals in sheets and kept them wet through the day.

"Some 63 pilot whales stranded ... but it looks pretty good, we've got 43 live ones," Department of Conservation ranger Steve Bolten said as the pod swam out to sea.

Bolten said one of the whales may have been sick, or their sonar may have led them into the shallow harbor and they couldn't find their way out again.

Camper Deanna Paddy and her family spent hours in the sea helping the whales, "trying to keep them as wet as possible and comfortable," she told Television New Zealand's One News.

One of the whales she helped died on the beach. "That's nature but we've still got others to try and help. We're just going to give them the best chance we can and hope for the best."

New Zealand has several mass whale strandings around its coastline each summer as they pass by on their way to breeding grounds from Antarctic waters. Scientists so far have been unable to explain why whales become stranded.