Ash Hilton and his son Henry Hilton, 5, queue for the monster slide.

Saturated and frustrated Nelsonians shivered in line for up to three hours for a turn on the 250-metre Monster Slide on Collingwood St, an event described by one as "clueless chaos".

Nelson mother Krystal Jenkins was "extremely annoyed" by the event organisation after spending over $100 to take her four children on the slide. Their ticket allowed them three turns but they only used one before giving up.

"It was horrible, we turned up at 9am which was the time we were told it started and it wasn't until 11am that they started letting people through," Jenkins said.

Alden Williams/Fairfax NZ Trish Casey and her daughter Ruby Casey, 8, enjoy the monster slide on Collingwood Street in Nelson.

Her children were "very upset" after the event.

"It is a good concept but they oversold the tickets, there was no way it could work with 2000 people," she said.

Another slider who did not want to be named said her children were "shuddering" as they waited between rides while staff struggled to keep up with the crowds.

"[The staff were] listening to their earpieces trying to make it work somehow, [they said] 'all boards left, all boards right, inflatable all to the left -- no all to the right', [it was] clueless chaos," she said.

"We asked for a refund but they said they deal with it on a case by case basis."

Trish Casey and her daughter Ruby, 8, enjoyed their ride down the slide but were not happy with the long wait.

"It was a very long wait, there are just too many people," Casey said.

There have been several complaints about the slide since an event that also drew criticism in Christchurch on Sunday.

Concerns about safety were also raised after a 54-year-old man was taken to Christchurch Hospital by the Westpac rescue helicopter with suspected spinal injuries after being knocked over by another slider at the bottom of the slide.

Three more reported injuries were sustained at the event in Nelson yesterday.

An 11-year-old boy was admitted to Nelson Hospital when he fell over and hit his head on the slide. He was reported to be in a moderate condition.

Two women were also picked up by ambulance staff on Collingwood St after hitting their heads while going down the slide.

Ticket prices varied from $15 for three slides up to $99 for 10 slides and special lane access, but many said they didn't get what they paid for.

Nelson woman Janet Watt, standing with her shivering family in the rain, said the slide produced mixed results from her family.

"I didn't get moving at all [down the slide] I ended up having to stand and walk the rest of the way down," she said.

"The lilo worked well [for her kids], it just depends on the equipment you have."

A lump in the road had also seemed to make it tricky for people to reach the bottom with enough momentum.

Logan Clarke, 13, said the slide did not have enough water.

"If you haven't got a board it's just so slow, they need to make it steeper and a higher volume of water."

Organiser Jamie Templeton, from event company Trill Productions, yesterday said too many tickets had been sold for the Christchurch event.

She said refunds would be managed by the ticketing company on a case by case basis.

"We can't give people refunds on the spot because we run through a ticketing agent. We have a process, they sign a form and we pass that on to the ticketing company and they get in touch and offer a refund. That's the process."