The temporary replacement for its crippled ferry Aratere has itself been involved in a maritime incident but KiwiRail says this will not cause any problems.
The Aratere has been out of service since it lost a propeller in Cook Strait on 5 November and will not sail again during the busy summer period.
KiwiRail says the Stena Alegra ferry, based in London, leaves for Wellington on Thursday for at least a six month charter.
It hopes the ferry will be sailing Cook Strait by the end of January.
The vessel had been sailing a route from Poland to Sweden and Interislander general manager Thomas Davis says it was involved in a minor grounding in the Baltic during atrocious weather.
"She's been in dry dock and had minor repairs completed. Those have been inspected by the classification society responsible for the ship and we've inspected it in dry dock.
"We're very comfortable that the repairs have been completed appropriately, and that that won't cause us any problem at all."
The replacement ferry can carry 350 passengers and 78 trucks, while the Aratere is capable of taking 600 passengers and 28 trucks.