The dozen remaining pilot whales that stranded at the mouth of the Okuru River south of Haast have been euthanised.
The Department of Conservation (DoC) was alerted to the stranding on Wednesday afternoon.
Thirty-eight whales in total were found - many already dead - and those that were alive have since been put down.
DoC Operations Manager Wayne Costello said the dangerous sea and lagoon conditions meant an attempt to re-float the whales could not safely be made.
"Unfortunately, the sea on the West Coast is typically rough and the strong tidal currents in the adjoining lagoon made it impossible for rescuers to safely attempt to re-float the whales, allow them to regroup and to try to get them back to the open sea."
"DoC staff working with Makaawhio iwi members and local people considered options for a re-float of the whales - but in the end, this could not be done without considerable risk to both whales and people.
"Those with the whales did all they could to keep them comfortable by getting them upright, cooling them and protecting them from sun and wind."