Wellington residents are outraged after the local Water Whirler sculpture was broken after a man tried to climb it.

The thin structure has bent and snapped under the weight of a man in his twenties dangling off it.

He was taken to hospital with moderate injuries after the pole hit him on the head as they fell into the ocean.

Lambton Ward Councillor Nicola Young is also a member of the Wellington Sculpture Trust, and says the man's ruined the Whirler for the rest of Wellington and its visitors.

"I did think this is natural justice that the man got injured. What a stupid thing to do."

She says the sculpture has been under maintenance for the last six months.

"And they were just weeks away from completion, which would have included a new buffer zone to stop morons like this from coming on and damaging it."

Salvage crews have been called in to retrieve the thin structure from the bottom of the ocean.

Len Lye Foundation director Evan Webb says it has immeasurable artistic value.

He says many people have put considerable hours of effort and work into realising it.

"It's very disappointing. In fact, it's very upsetting to have a work like this so wilfully damaged."

Webb says he doesn't think the damage will be irreparable.

He says if it's just the pole that's damaged, it's possible to build another one.

"I do wish that people would respect public sculpture and not tamper with it, but this is the world we live in."