Passengers on the Manly Ferry were stranded for hours after the ferry broke down near Manly on Thursday evening.

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.

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