Many within the family are keen divers and Mr Munro said that had the conditions been better that day - December 18 - they would have gone out and attempted to get photos.
He said locals around nearby Te Arai Pt and the Pakiri river had also reported shark sightings in recent weeks.
The reported sighting follows that of a 4.5m great white in the Waitemata Harbour on Monday.
A family fishing from a 6m vessel near Te Atatu, West Auckland, hooked the predator on a fishing line.
A witness said the shark jumped high out of the water, snapping the line.
That sighting has led to the Department of Conservation putting out a warning to those out fishing, kayaking and kite-surfing in the area.
Shark expert Dr Malcolm Francis, of the National Institute of Water and Atmospheric Research (Niwa), said both sightings sounded legitimate.
School sharks and bronze whalers were more commonly seen, he said, and it was very rare to see a great white jumping in New Zealand seas.
Dr Francis said there were "thousands" of great white sharks around the country - including very young ones - that could reach up to at least 6m in length.
"They're born about one and half metres long and they take 10 to 15 years to reach maturity.
"You've got a lot of smaller animals around the coast - mostly feeding on fish.
"You'll get a lot of those little ones around the Kaipara and Manukau harbours."
