Emergency services raced to the city centre just before 11am on Friday.
The body was found in the river at the botanic gardens near North Hagley Park off Riccarton Ave.
"At this stage of the investigation there is nothing to suggest the death is suspicious," said Detective Senior Sergeant Craig Johnson.
"Police will continue to conduct enquiries over the coming days to determine the full circumstances of what occurred.
"Cordons are expected to be lifted in the coming hours."
Police, Fire and Emergency NZ (Fenz), and St John have been called to the scene.
Wells said a fire truck was assisting police and St John at the scene.