Project Jonah says the rest of the pod of 53 has made its way back out to sea.
"Beaches across Golden Bay have been checked for whales this morning. Of the 55 whales that stranded yesterday, 15 have re-stranded and six have been found deceased," a Project Jonah spokesperson said.
Volunteers and Department of Conservation staff are keeping the remaining whales cool and comfortable until the high tide this afternoon.
Project Jonah said the group was near the tide line so there would only be a small window to attempt a refloat.
The organisation is welcoming any help from the public, with a plea for people to bring wetsuits and their own supplies.
Those working at the site were stood down by 10pm yesterday and returned at first light.
The Department of Conservation said Farewell Spit, where whales frequently strand at the top of the South Island, "is a naturally occurring "whale trap" that occurs along a migratory route for long-finned pilot whales in New Zealand".
"The spit hooks around the northern entrance into Golden Bay forming extensive intertidal sand flats flanked by gently shelving waters offshore. Whales may be easily deceived and caught out by the gently sloping tidal flats and a rapidly falling tide.
"Pilot whales have strong social bonds and if one whale heads into shallow water, the rest of the pod will follow due to their natural instinct to look after one another.
"We will continue keeping the whales cool and comfortable through the morning and are aiming for a refloat on this afternoon’s high tide. These whales have re-stranded along the high tide line, which adds to the complexity of the refloat.
"If you are able to come and help (on Friday), please be aware that only people in wetsuits will be able to assist with the refloat this afternoon.
"If you do not have a wetsuit, you can still help this morning, but please follow all guidance given, as we do not want to overcrowd the whales."
Project Jonah said the conditions at Farewell Spit can be harsh, with strong sun and high winds, and there are no food or drink facilities at the spit.
• Anyone attending the stranding must be fully prepared. To find out more about what to expect, go to www.projectjonah.org.nz/golden-bay-strandings.
- RNZ and Allied Media
