It's a mystery why a big healthy sei whale got stranded, but newly-released documents show the effort and detail that goes into whale rescue attempts.
In the wake of an Easter whale rescue involving former All Black Ali Williams and surf life savers, documents released about a fatal December stranding showed a sei whale seemed to be improving just minutes before it died.
A big whale carcass like that of the sei can take three months to decompose.
Department of Conservation documents show the 30 tonne whale was reported to be in distress at Golden Bay's Farewell Spit at 2pm on Friday, December 4.
Four DoC staff arrived, put wet sheets on the whale and measured the animal.
Local iwi and about 30 volunteers worked into the night, keeping the whale moist and cooling it off with cold water.
There was no sign of trauma or injury, and the whale appeared to have been a healthy weight.
The incoming tide reached the animal just after 8pm but by then whale was breathing from just one blow hole.
The whale flipped itself up on to its stomach at 8.47pm.
"So hopefully it has the energy to swim off tonight," DoC ranger Amanda Harvey told a colleague at the time.
DoC staff arrived for the night shift at 9pm but the whale died about 25 minutes later.
The conservationists shared their disappointment in a WhatsApp channel created for the whale rescue.
To remove the carcass, 200 metres of rope was needed.
Official information released to the Herald showed the main safety issue for people was the potential danger from the creature's very large tail flicking.
The male sei whale was 13.4m long from its upper jaw tip to the deepest part of its fluke notch.
Sei whales are the third-biggest whale and this one was big even for its species.
DoC staff and volunteers returned to the site with ropes and floats.
The dead whale was refloated and plans were made to tow it out to the Farewell Spit tidal flats at high tide, around 2pm the next day.
A larger boat had to be contracted for this work, due to the size of the whale.
A Takaka DoC park ranger and marine species adviser drew a sketch of the net, rope and floats.
Meanwhile, vast amounts of gas were building up in the dead whale for days.
An email from a DoC ranger showed the carcass was expected to take three months to decompose.
"On previous occasions it has taken about three months for a whale carcass to fully decompose," a park ranger said.
"The nutrients feed the worms which fatten the godwits and other waders," he added.
Over the Easter break, Ali Williams and global toy company Zuru founder Nick Mowbray refloated a whale.
Mowbray told the Herald he and Williams were flying from the Bay of Islands when they saw the whale.
Mowbray said the pair circled back and landed. The beach was empty when they began efforts to save the animal.
Local surf life savers with rope joined Williams and Mowbray.
Video of the incident showed the men pulling the whale by its tail to free it from the sand.
Whale rescue charity Project Jonah said the techniques used risked "significant damage" to the whale and put the rescuers themselves in danger.
Meanwhile, police today said a crew of rural North Auckland staff had been trained in what to do in the event of a whale stranding.
Police said officers based in Wellsford, Helensville, Warkworth, Orewa and Kumeū spent a day with Project Jonah.
"Our staff across the country, particularly in rural coastal areas, are often among the first to know about strandings, so it makes sense they are able to help."