Department of Conservation staff say there is nothing more that can be done on Monday night for the whales in danger of re-stranding near Farewell Spit.
The 46 pilot whales were re-floated at Puponga but were still in fairly shallow water.
About 250 DoC staff and volunteers were to leave the area for the night and would check again on Tuesday for the whales. It was hoped they would make their way into deeper water and not re-strand.
DoC's Takaka services manager John Mason warned that time was running out.
"There's bad weather coming tomorrow, which I think is going to make a re-float impossible. So really today I think is their last opportunity."
"We do monitor the whales daily - we look at their condition, we look at their behaviour and if it looks as though stress or ill-health is taking its toll, then we do think of our other options."
On Monday, more than 100 volunteers arrived at Farewell Spit to help save the whales.