KEY POINTS:
Leaping from the water and slapping their tails on the surface, a humpback whale and her calf thrilled onlookers with a display of acrobatics on Auckland's doorstep.
Scientists and whale watchers are wildly excited by the extremely rare sighting of a humpback in the Hauraki Gulf.
Explore NZ's Auckland Whale and Dolphin Safari spotted the mother and calf north of Waiheke Island on Friday, and thought they had come into the gulf to feed on their way to the Antarctic.
"Everyone was really excited ... it's incredibly rare for them to come so far in," said the expedition's senior master Keith Algie.
Department of Conservation marine scientist Dr Mike Donoghue said there had been only five or six confirmed sightings in the Hauraki Gulf in as many years.
After whaling stations were established around New Zealand from the late 19th century, the whale population - particularly humpbacks - was hunted almost to extinction.
Today the species is considered to be endangered.
Mr Algie said it was possible the mother and calf would be regular visitors to the area, with its "vast menu" of food.
The safari boat had a full load of passengers at the time of the sighting, and Mr Algie said they were left speechless by the display.
He said the whales performed some stunning acrobatics.
They hurled their entire bodies out of the water, and what appeared to be synchronised tail-slapping entertaining onlookers.
Dr Donoghue was thrilled to hear of the sighting, and said he hoped the whale would be back.
"How absolutely splendid. She's potentially a new chum, but if not then we'll still be able to find out a little more more about her so it's really good news," he said.
"It's a good indication that the population is slowly recovering."
Photos of the whales' distinctive tail marking would be sent to the South Pacific Whale Research Consortium for closer inspection.
