A 15-year-old boy's managed to avoid trouble after being swept down Ngatiawa River in Tararua Forest Park

Heavy rain caused the river to rise rapidly while he was trying to cross, but he managed to reach safety on the opposite riverbank, where he activated his personal locator beacon.

The friend he was with walked to the end of the track to wait for Search and Rescue crews.

Constable Alex McCormack says the boys did a lot of things right, but conditions can change quickly.

Constable McCormack says the fact they're okay is a real relief given what the river was looking like.