An Australian surgeon has helped more than 60 people flee a sinking ferry off the coast of the South African city of Cape Town.

Key points: David Nicholson helped evacuate passengers when the Robben Island Ferry took on water

David Nicholson helped evacuate passengers when the Robben Island Ferry took on water He described scenes of panic and confusion as the situation unfolded

He described scenes of panic and confusion as the situation unfolded The South African Maritime Safety Authority has launched an investigation into the cause of the incident

The ferry, named Thandi, carries people from Cape Town to Robben Island, the former site of a prison where Nelson Mandela, Jacob Zuma and other notable figures were imprisoned during the Apartheid era.

David Nicholson, a 48-year-old orthopaedic surgeon from Newcastle, was on board the ferry which was headed to Robben Island when it struck rough seas.

David Richardson and his wife Emma Charls-Nicholson were on their way to visit the museum at Robben Island. ( Supplied )

"We'd been going through the swell pretty hard and waves were breaking over the front of the boat, and [I noticed] some of the windows at the front of the boat were leaking," Dr Nicholson said.

"It became pretty obvious that they weren't designed to take on waves and eventually water started pouring in through those front windows."

He described scenes of panic and confusion as the unfolding situation became clear to the other passengers onboard.

"People were starting to worry if everything was OK — A lot of people were looking pretty distressed," he said.

Sorry, this video has expired Dozens abandon sinking ferry of Cape Town, South Africa

Dr Nicholson said it became evident the nose of the vessel was slowly becoming submerged as it took on more water.

"Once it became really obvious that it was down, the crew called for everyone to get their life-jackets on," he said.

"It took a bit to calm people down at that stage. People were really starting to freak out."

'People were really worried no-one would turn up'

Dr Nicholson said it seemed like it took a long time for help to arrive as the situation unfolded. But when help did arrive, he said the rescue service was quick to usher everyone to safety.

The National Sea and Rescue Institute (NSRI) said at least 10 rescue boats, two helicopters and various medical and dive crews responded to the stricken ferry.

Another Robben Island ferry, Madiba 1, was also at the scene.

"I'm sure they were getting there as fast as they could but … people were really worried no-one would turn up," Dr Nicholson said.

"On arrival on the scene the ferry was found to be listing to one side from water intake from unknown causes and some of the passengers were found to be in life rafts and the remaining crew and passengers were on the deck of the casualty ferry," the NSRI said.

At least 10 rescue boats, two helicopters and several crews responded to the ferry, the NSRI said. ( Supplied: NSRI )

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Dr Nicholson was one of the last to leave as rescue crews transferred the passengers to another vessel.

"The entire process probably took about half an hour to get everyone off the [sinking] boat," he said.

The NSRI added that a female passenger who was aboard Thandi was treated for back pain, and a female passenger from Madiba 1 was treated for anxiety.

The South African Maritime Safety Authority announced an investigation into the cause of the incident, which Dr Nicholson said he thinks is greatly needed.

The incident has prompted many people to take to social media to comment on their past experiences travelling to Robben Island.

"A few weeks back I was on this small ferry. How could they even thinking of sending this thing out in the weather," Deon Collison from Cape Town said on Facebook.

"One time and maybe the only time I was on one of these. It was windy and the sea was high … I can't even begin to imagine the terror they must have gotten," political communications student Joy Buria said.

"Let me affirm that these boat rides on windy days like today are so scary and should simply not be allowed."

Thousands of tourists each year make the journey from Cape Town to the World Heritage site at Robben Island.

Dr Nicholson said the passengers on board the ferry appeared to be mostly tourists from a mix of countries.