'Our biggest worry is getting ill and wondering if we'll ever get home.'

Australians stranded onboard a cruise ship in waters off Panama say they are living a nightmare with four passengers dying from COVID-19 and hundreds more now unwell.

There are 135 sick passengers on the Zaandam cruise with two confirmed cases of coronavirus.

New South Wales couple Peter and Carole Burke say they are trapped in their tiny cabin with one window.

"We are not allowed out of our cabin. We can only open the doors to collect meals and return trays when we finish with a mask on," Mrs Burke told 9News.

"We have had one 30 minute on deck fresh air exercise two days ago."

The Burkes from Port Macquarie in the state's north coast boarded the luxury liner in Buenos Aires in Argentina on March 7 this year.

A week later on March 14 they docked at Punta Arenas in Chile. That same day they were told the cruise was being cut short and that they could expect to return to Australia on March 21.

The ship then left Chile but was denied entry at ports in Peru and Ecuador. It eventually anchored off Panama where they remain.

A second ship, The Rotterdam, is now anchored next to the Zaandam as a rescue vessel. But the Burkes aren't allowed to leave.

"Our biggest worry is getting ill and wondering whether we'll ever get home to Australia," Mrs Burke said.

The Department of Foreign Affairs is urgently trying to contact Australians on board, but the Burkes say they are yet to hear from the government department.