A day out on the water with mates turned into a nightmare when a man was swept out to sea on the notoriously dangerous Manukau Harbour.

The victim was one of three people riding on a jet ski being towed by a vessel when the jet ski overturned and all three men ended up in the water, Coastguard Northern Region said.

Everyone got back onto the jet ski safely, until someone spotted the jet ski's key in the sea - and immediately dived in to retrieve it.

"One gentleman has dived in and ended up being swept away," duty officer Nico Doodeman said.

Advertisement

The victim was swept out down the channel and the alarm was raised by the others in the group just after 6pm.

A nearby resident, who asked not to be named, captured the moment the rest of the group waited on the water as authorities worked to find their mate.

READ MORE:
'I owe them my soul' - NZ Coastguard starts 2019 annual appeal to raise $20 million
Coastguard issues advice after three-hour search for man found onshore
Homunga Bay rescue: Coastguard tows boat to safety amid massive chop
Premium - Allan Turia is Coastguard's Rescue Vessel Volunteer of the Year

The resident said he was not sure what had happened at that point, but could see a helicopter over the area.

A police eagle helicopter, an airport hovercraft and two rescue vessels were called in from Papakura and Titirangi.

The Titirangi rescue boat was not needed in the end; as the Papakura rescue boat managed to find the victim and pull him to safety out of the water.

'HE WOULD'VE DIED'

Doodeman said the victim had been wearing a life jacket - something that most definitely saved his life.

Advertisement

"It's our belief he would've died if he didn't have a life jacket," he said.

A map released by Coastguard shows the man was swept out about 800m from the jetski he and his friends were on on the Manukau Harbour. Image / Coastguard Northern Region
A map released by Coastguard shows the man was swept out about 800m from the jetski he and his friends were on on the Manukau Harbour. Image / Coastguard Northern Region

A post online said the man was "incredibly tired" when he was pulled to safety.

"His life jacket meant he was still floating when Papakura Rescue One arrived on scene."

A tracking map released by Coastguard Northern Region shows exactly how far the man was swept down the channel.

Doodeman estimated he was found about 800m away from the jet ski and spent the better part of an hour - about 45 minutes - battling choppy seas.

The other key factor in alerting authorities so quickly - and ultimately saving the man's life - was having a locator beacon; which the other men in the group activated as soon as the man was swept away.

Police confirmed the man was taken to hospital in a moderate condition.