The 12 surviving pilot whales out of a pod of 38 that stranded themselves on a remote West Coast beach have had to be euthanised.

Photo: Facebook/Project Jonah New Zealand

The pod stranded themselves some time on Wednesday on either side of the Okuru River mouth, south of Haast.

The surviving whales were comforted by Department of Conservation rangers, local iwi and other volunteers today but an attempt to refloat them at high tide this afternoon was not possible.

Rough seas and strong tidal currents in the adjoining lagoon meant a rescue carried too much risk.

A DOC spokesperson, Wayne Costello said euthanasing the whales was the most humane thing to do.

"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...this is a sad outcome," he said.