A cruise ship which ran aground on rocks in Fiordland's Doubtful Sound last week will restart trips on Tuesday afternoon.

The RealNZ-operated Fiordland Navigator ran aground near Crooked Arm in Doubtful Sound last Wednesday.

All 67 passengers and crew on board were evacuated, with one person sustaining minor injuries.

The boat's hull was breached and it took on water, but it was refloated later that night and returned to its berth at Deep Cove.

Real NZ chief conservation officer Paul Norris said final repairs had been made to the vessel, and it was cleared to return to service on Monday.

"All regulatory authorities have been supportive of our approach to bring the Navigator back to service and kept up-to-date with progress. We are excited to welcome back our first guests on the Fiordland Navigator's overnight experience in Doubtful Sound this afternoon."

Norris said there were external and internal investigations underway into the incident.

The Transport Accident Investigation Commission said it was investigating, talking to witnesses and collecting evidence from the site.

Chief investigator Naveen Kozhuppakalam said the ship was also investigated back in 2006. However, he said it was too early to draw any possible links to the latest incident.

Kozhuppakalam said groundings were considered serious because they could damage the hull and create a loss of structural integrity, which could potentially result in the vessel sinking or capsizing.

"The commission's investigation should draw into any particular lines of inquiry that [the grounding] has been a systemic issue that we might identify, but at this stage it's too early to comment on any of that.

"What we do know though is that the evacuation was quite successful. Once the vessel grounded, the crew responded well and the passengers were safely evacuated, so there was a good outcome."

It could be up to two years before the marine safety inquiry was completed.

Main image (RNZ/supplied/RealNZ): The Fiordland Navigator.