Wellington waterfront's Water Whirler sculpture appears to have snapped from the weight of a man dangling off it.

The Len Lye sculpture had been undergoing maintenance and was due to be back in action this month.

But a man has climbed up the thin structure, bending it and eventually breaking it.

A Wellington City Council spokeswoman says the spike hit the man in the head and he was lucky to miss the rocks beneath him when he fell.

The man's been taken to hospital and the scene of the incident has been cordoned off.

Wellington City Council waterfront specialist Fraser Ebbett said the man was being egged on my onlookers.

"He's climbed to the top and it's bent right over. It's obviously got to a point where it couldn't hold his weight and has snapped at the base.

"He has proceeded to fall in the water and at the same time the pole has made contact with his head quite heavily and caused a bit of blood."

A Wellington Free Ambulance spokeswoman said the man was aged in his 20s and has moderate injuries.

The incident happened at about 3pm. Police have been notified and the area has been cordoned off.

Ebbett said salvage crews had been called in to retrieve the pole, made of metal and fibre glass, which was now lying on the sea bed.

"We are hoping to get the sculpture up and running again but it really depends on us retrieving the pole from the ocean and seeing its state."

He said it wasn't the first time someone had climbed the structure, but not like this.

"I've never seen anyone get as high as he has."

Ebbett said obviously they never liked seeing anyone get hurt, but the situation was still frustrating.