Volunteer Zainab Aziz aged 12 helps to keep the whale wet while waiting for the tide to come in.

A Minke whale beached in Auckland harbour for seven hours is now swimming free and "heading in the right direction".

The sea mammal, believed to be the same whale seen up an Auckland creek on Tuesday, was found beached about 7am on Wednesday on Pt Chevalier beach near central Auckland.

THE RED BOATS The whale was spotted swimming beside near the Riverhead Tavern near Auckland on Tuesday.

Initially believed to have been a Bryde's whale, it was later formally identified as a Minke.

About 2.30pm the whale managed to re-float itself and was swimming freely, Department of Conservation (DOC) spokesman Nick Hirst said

"The whale is floating, it's off the ground. It's swimming and it's making good speed.

ROSE REES-OWEN/FAIRFAX NZ Volunteers are working to keep a beached whale in an Auckland harbour wet.

"At this stage, it's heading in the right direction - out towards open water."

A DOC boat was following the whale's progress, he said, with two DOC staff and University of Auckland marine scientist Dr Rochelle Constantine on board.

The boat would stay with the whale out to open water, Hirst said.

ROSE REES-OWEN/FAIRFAX NZ The whale is beached near Pt Chevalier in Auckland.

"Fingers crossed it's going to be okay," he said. "The indications are positive."

The whale was discovered beached early on Wednesday morning, and is thought to be the same whale that, on Tuesday, was seen struggling more than a kilometre up a narrow inlet on the upper Waitemata Harbour called Rangitopuni Creek.

Volunteers flocked to the scene at Pt Chevalier on Wednesday morning to assist the whale and try to keep it wet.

@publicaddress/TWITTER The whale spotted in an Auckland river is now stranded near Pt Chevalier.

General manager of the marine mammal charitable organisation Project Jonah Daren Glover said he was alerted to the stranding at 7.30am on Wednesday.

Glover said he was "cautiously optimistic" the whale would survive.

"If it's alive there's always a chance [but] there may be problems internally where it's been lying on the beach for several hours."

Andrew Somers of The Red Boats, who saw the sea mammal in the inlet on Tuesday, said he thought it was eight to 10m long.

"It's very unusual to see one up the river. I've never seen anything like it," Somers said.

Somers said the whale almost beached itself on the mudflat two or three three times, but managed to wriggle itself free.

Minke whales were the most common of the baleen whales to become stranded on New Zealand shores.

Anyone who sees the whale in distress can call 0800 DOC HOT (0800 362 468).

Earlier this month a southern right whale was seen swimming just metres from shore in Auckland's in Mechanics Bay.