The man and woman went into the river near Albert St in Palmerston North.
A search is under way this morning for a man swept away in the Manawatu River trying to rescue a dog.
The Police National Dive Squad, volunteer LandSar, swift water rescue teams and a helicopter are searching the water around the Fitzroy Bend in Palmerston North.
Local resident Catherine Nolan said the search was unfolding outside her window.
She said emergency services and a helicopter had been around until after 1am and resumed their search at 5.30am.
She said she'd got into trouble boogie boarding down the river one New Year's Day, when she was caught in some pylons.
"It drags you in, but it drags you under and you get caught up in all the branches and stuff."
The water pressure made it hard to get out.
She said it was a treacherous spot.
"Unless you know to keep well away from the pylons you can really get into trouble. If he got caught and swept, you don't have any control if you're in a certain piece of the flow of the river."
Inspector Dave White said the river level had dropped and there was no wind this morning.
"The search is fully resourced and the focus is on finding the man," said White.
Last night the search focused around Albert St in Palmerston North where the man and woman got into trouble in the water.
Police said emergency services were called at 6pm.
A woman was rescued and received medical treatment from ambulance staff before being taken to Palmerston North Hospital with non-life-threatening injuries.
It is believed the man was swept down the river after entering the water to rescue a dog.
A helicopter and riverbank search for the man continued into the night, but the search on the water was postponed because of the lack of light.
Residents have been warned to expect a police presence as the scene is examined.