Around 200 workers at the Lyttelton Port took to the streets to protest pay and safety concerns on Thursday.
The Rail and Maritime Transport Union have been protesting since last Tuesday, concerned about their eight hours on eight hours off rosters.
One port worker said operating the heavy machinery is too dangerous when the workers might've only had a few hours sleep.
Workers had planned to walk through the Lyttelton rail tunnel, but were confronted by police at the scene.
The protesters took it to a vote and were all in favour of leaving peacefully.
Strike organiser John Kerr said their picketing protest last week had been ineffective and they needed a more creative way to publicise the strike.
He said something needed to be done, and he couldn't understand why the company was acting the way it was.
"Our members are vital to the running of the port," Kerr said.
"Any good manager will tell you his or her staff are their biggest asset. Lyttelton Port management don't seem to understand that."