UPDATED 3:01:The Christchurch man who was spotted clinging to a bridge pillar has had a lucky escape.

Police conducted a water rescue to save the man who was hanging onto the pillar of a bridge on the Northern Motorway near the off ramp to Kaiapoi.

Police were alerted to the incident just after lunch, by a member of the public who spotted the man in the water. 

Acting Senior Sergeant Jim Currie said it was not an easy rescue.

"Coastguard were brought out and they couldn't get the boat close because of the shallow nature of the water there, so an inflatable was brought out."

Jim Currie said it is unclear how the man came to be in the river.