Fullers staff are getting a pat on the back for saving a 22-year-old man who'd fallen into the water from Princes Wharf in downtown Auckland.

Emergency services were called to Princes Wharf just after 5am.

Senior Constable Martin Renouf of the Police Maritime Unit said the crew of Fullers ferry Te Kotuku heard someone in the water shouting for help.

He said by the time police got there, ferry staff were retrieving him from the water.

"By the time we got there the ferry was pulling a male person from the water who had been in the water apparently for some time, possibly intoxicated."

Renouf said police are investigating whether the man was pushed rather than fell.

He is believed to be mildly hypothermic and has been taken to hospital.

He said luckily the ferries are running early for the Marathon.

"The ferry did a very good job, Fullers ferry Te Kotuku and the crew on there did a good job locating him and then pulling him from the water."