Manly Ferry left drifting after mechanical issues

The ferry was around 30 metres from Manly Wharf, witnesses said, when it suddenly stopped and started drifting.

Transport authorities organised for two ferries to pull alongside the broken-down Queenscliff, and planned for passengers to walk across a plank to the working boat.

However, this idea was hampered by rough swells, and passengers were told a spare part would be sent to the ferry in a water taxi.

As passengers waited, other ferries were also delayed by the "mechanical issues".

Harbour City Ferries, which operates the service, said the issues unfolded on the 6pm Circular Quay to Manly service, "on approach to Manly".

"The vessel, the Queenscliff, dropp[ed] anchor near Manly Wharf. We are monitoring the situation and will provide updates as soon as possible," the ferry operator said in a statement.

"Harbour City Ferries apologises for the inconvenience. The safety of our passengers is our highest priority and we will continue working hard to get everyone back to shore as soon as possible."

Maciej Skrzyszewski, from Queenscliff, boarded the ferry to get home from work and was sitting on the upper deck as it approached the wharf.

As it got closer, it started braking, then there was a noise as it abruptly stopped.

Some of the passengers rushed outside to see what was going on, while others remained relaxed through what would become a lengthy wait.

Mr Skrzyszewski said the captain kept the passengers updated every 15 minutes, and they were offered free tea and coffee.

"We were just waiting for other boats to try to rescue us, so we could move from one to another, but it was a little bit too dangerous to do that," he said.

"Everyone thought that the first boat that was going to come would take us, then they said another one would drop passengers from Manly Wharf and come and pick us up.

"They tried to connect, but it was a bit rough for them. They opened the small cafe for people to get anything they want, so people could get some tea or a coffee or water."

He said the crew was "very comforting to everyone", so most of the passengers were relaxed during their long wait.

Passenger Patrick Clarke said an alert siren went off before the boat, which can hold more than 1000 people but was not packed at the time, began to drift.

He said it was anchored around 200 metres from its destination.

"They had to anchor us otherwise we were going to run into other boats," Mr Clarke told AAP after getting off the boat on Thursday night.

"There was just growing frustration because, you know, you're so close."

Mr Clarke said two separate rescue attempts were made but staff could not be sure it was safe enough for passengers to move from the damaged ferry to a working vessel pulled up alongside.

He said a spare part was eventually brought via water taxi, before passengers disembarked around 8.40pm

"They tried really hard. They offered everyone coffee and everything," Mr Clarke said of the ferry staff.

"At the end of the day they just said it's all about the safety of passengers."

The ferry finally made its way to shore at about 8.30pm.

with AAP