A person has been successfully rescued after falling overboard from a Bluebridge ferry in the Cook Strait. Emergency services responded quickly to the incident.

KiwiRail's Interislander ferry service is anticipating hours-long delays over the weekend, attributed to higher than usual freight and passenger numbers across the Cook Strait.

Bluebridge Cook Strait Ferries said a fault was identified on board the Connemara Saturday morning.

Despite the Psa-v bacteria entering New Zealand 16 years ago, the South Island has successfully kept the kiwifruit-killing disease at bay through strict quarantine rules and testing, with the Cook Strait acting as a natural barrier.

Police are conducting a search operation in the Cook Strait after a person reportedly went overboard from a ferry, though authorities are not seeking anyone else in relation to the incident.

The New Zealand government will publicly release the findings of an inquiry into the catastrophic failure of the Moa Point wastewater plant next week. This comes just over five weeks after a massive backflow of sewage flooded the plant, which has been discharging millions of litres of raw sewage into the Cook Strait daily since February.

Overseas tour operators report that the perceived unreliability of the Cook Strait ferry service is causing international tourists to bypass New Zealand's Wellington region and the Top of the South.

Sailings for the Connemara Cook Strait ferry have been cancelled for a sixth day, with the company uncertain if the ship will be repaired before the weekend.

Bluebridge is indicating strong southerlies could cause delays and cancellations.