KEY POINTS:
Department of Conservation workers who last night buried the 37 stranded pilot whales in Northland will remain on standby over the weekend in case 40 surviving whales try to return to shore.
Yesterday's stranding of around 80 whales near Marsden Point was the largest in Northland for several years.
Rescuers, including staff from the nearby oil refinery, said cool weather and a favourable tide helped them to refloat half the pod.
"That's a huge effort," said department ranger Bryce Lummis.
"What was lucky was, when they were found it was close to high tide. The tide and the weather actually worked in our favour."
Mr Lummis said rescuers had around 12 hours from the time the whales stranded yesterday to get them swimming back out to sea.
One young whale that separated from the refloated pod was put down to try to prevent the pod from restranding.
Coastguard and boaties kept watch over the refloated survivors as they swam toward the Hen and Chickens Islands.
Ngati Wai helped decide how to manage the dead whales.
New Zealand Refinery Company Marsden Point emergency services manager Ben Trail was called to the scene by a worker who spotted two whales on the beach about 8am.
"As I was going down I noticed there was a big pod of whales further down the beach that I didn't know about," said Mr Trail. "I couldn't believe how many were there."
He said up to 150 people gathered to refloat the 40 whales.
"We didn't actually count them because everybody was putting them in the water, holding them in the water and getting them out to sea," said Mr Trail.
"Some people were emotionally disturbed by it because of the numbers."
He said rescuers were particularly upset about a baby whale - less than 0.5m long - that had died on the beach.
"That one seemed to be the one that made people sigh and gasp."
The refloating was Mr Trail's first: "I hope that I never go to another one."
