The man who broke Wellington's famous Len Lye Water Whirler sculpture by climbing it says he was bored and decided to practice his gymnastics.

Hunter Macdonald told Stuff he was a "show-off" and was egged on by the crowd who formed to watch him.

"A crowd started to form, sort of egging me on ... I was sort of taking it further and further seeing how high I could go, seeing how far I could push the sculpture."

He said he never meant to break it and believed it was strong enough to hold his 80kg frame.

Macdonald told Stuff it was a "kick to the ego especially because I was there kind of showboating".

"But that's who I am, I'm a show-off, but it bit me on the butt this time."

Hunter Macdonald broke Len Lye's Water Whirler sculpture when he climbed up it.

He said he had taken up gymnastics as a hobby recently.

The fall left him with two gashes to the head which needed stapling and cuts to his left leg.

"That thing was like a big 20m baseball bat striking me on the back of the head."

As for the cost of fixing the sculpture, which cost $300,000 at installation, Macdonald said he was never going to get a pay-cheque of that size but would do whatever was required to make up for it.

"I apologise for defacing that, that wasn't my intention," he told Stuff. "I'm willing to do whatever's required you know, because that's the best way to show remorse."