Police have confirmed the body washed up in Karaka Bay this morning is that of a 19-year-old who went missing while swimming in the Hutt River on Thursday.

A member of the public reported the find to Wellington police at around 7am. Police recovered the body and have formally identified it as the missing teenagaer.

Karaka Bays resident Sue Barnett said she woke up to a commotion on the beach opposite her house.

"When we got up there were about six police cars, and a dozen policemen, and the whole beach was cordoned off.

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"There was a large object on the beach, and we realised what had happened."

Ms Barnett said the teenager's body was on the beach for about an hour before police took it away.

The tragedy was a grim reminder of what the local river was capable of.

"We've had quite a lot of rain, and when the Hutt River floods, it really floods," she said.

"We get quite a lot of logs and things caught up in it."

Police are not naming the deceased at this stage. The family has been informed and is requesting privacy.

Police thanked all of the organisations who helped in the search, including LandSAR, the Hutt Community Emergency Response Team and the Upper Hutt Community Rescue.

A friend of the 19-year-old was frantically searching and calling out on the bank of the Hutt River on Thursday after the man went for a late night swim.

Search teams are scouring the Hutt River mouth and harbour after a teenager was washed away last night. Police said the 19-year-old and a teenage friend went swimming in the flooded river around 10.30pm near Belmont School.

Search teams scoured the rain-swollen Hutt River mouth and harbour. Sergeant Anthony Harmer said when one of the teenagers got out of the water he could no longer find his friend.

Greater Wellington Regional Council river ranger Travis Moody said the river was at its peak when the 19-year-old entered the water at about 10pm.

"It gets quite ferocious even in a smaller rain event like that. Any time the river's up you don't want to get in the water.

"It's a raging torrent basically. You'll have big boulders underneath the water moving along with that flow."

Moody said the man would have struggled to keep his head above water in those conditions.

"Even if you did get to the side, you'd have to deal with a whole lot of vegetation.

"It's pretty easy to get pulled under when it's like that, poor guy."

A drone was also used in an attempt to find the teen.