Moments later a shark's fin can be seen racing past.
The close encounter sets of a flurry of splashing from the man filming the video, who appears to be making a hasty retreat to the shore with his daughter.
Although it's not clear in the video, the man's daughter commented on YouTube that her father was "hit by the shark".
The NZ National Institute of Water and Atmospheric Research says the sharks that people are most likely to spot in local waters over summer are the Bronze whaler, Blue shark, School shark and the Spotted dogfish.