An internal investigation by Interislander reveals it was the fault of one of their officers which nearly caused the ferry Arahura, to hit a recreational fishing vessel.
The company say the officer failed to maintain navigational watch, despite being warned about the boat's presence just before the ferry had to make an emergency manoeuvre.
The officer was stood down following the incident at Karori Rock on 20 February.
Interislander says appropriate action has since been taken and the officer has now been re-employed.
Maritime New Zealand is continuing its own investigation.