New Zealand's Department of Conservation said on Saturday that it has successfully re-floated 14 pilot whales at North Island's Far North beach, but another seven stranded again and had to be put down.

The whales were part of a large pod that became stranded at Spirits Bay, east of Cape Reinga, on Wednesday morning.

Between 40 and 50 had already died and heavy seas prevented DoC staff from refloating the mammals from that beach.

They was transported more than 50 km south to Rarawa Beach on Friday. DoC says three whales died during or after the journey, and the remainder were released about 7.30 p.m..

While some swam away immediately, others were herded out by boats and jetskis.

In August, about 60 pilot whales were stranded on the Karikari peninsula in the Far North. Fewer than a quarter survived.