Nearly pilot whales have stranded themselves on a beach on New Zealand's South Island.

Department of Conservation area manager Andrew Lamason says two dozen of the 198 whales that were found beached on Friday have already died. The animals stranded themselves on Farewell Spit, a famous spot for whale beachings.

About 80 conservation workers and volunteers are trying to refloat the whales as high tide rolls in. But with such a vast number of animals stranded, workers are bracing for days of arduous work to move the whales back into the water.

Whale strandings are common during the New Zealand summer. Experts describe Farewell Spit as a whale trap due to the way its shallow waters seem to confuse whales and diminish their ability to navigate.