Greymouth rescue teams have been stood down from saving what was initially believed to be a person in the water after the floating object turned out to be a log.
A police spokeswoman said it was confirmed the "person" they were trying to save was not a person but a log.
"Which is a good thing really," the spokeswoman said.
Emergency services were called at 7.45pm after a police officer thought they had spotted the person in danger off Packers Quay beach.
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The object had been bobbing up and down about 500 metres from the shoreline.
A police spokeswoman told the Herald police had been assisted by Canterbury West Coast Air Rescue Trust and Surf Life Saving New Zealand.