Fishermen swept into freezing Manukau Harbour, one in water for 50 minutes

Four coastguard vessels, a rescue helicopter and police began a full-scale search. Photo / Supplied

A fisherman swept off rocks into the Manukau Harbour last night spent nearly an hour in freezing water before managing to swim to shore.

Four coastguard vessels, a rescue helicopter and police began a full-scale search just before 8pm when a man swam to shore after a large wave swamped two men and pulled them into the water.

Coastguard said one of the pair managed to swim ashore and raise the alarm.

But it wasn't until 8.40pm that the second man made it ashore - 50 minutes after his mate made it safely to land.

A Coastguard spokesman said the men were fishing at Whatipu, near Huia Bay, when they were unexpectedly washed into the water.

The first man was found by a member of the public when he reached safety at Whatipu.

The second man was understood to have come ashore on the same stretch of harbour.

Conditions were not believed to be particularly rough at the time of the incident.

Coastguard said a total of 10 volunteers from Papakura, Waiuku and Titirangi were on the water within half an hour but stood down when the missing man came ashore.