Eight people were rescued from Doubtful Sound after the 12m catamaran they were in sank in poor weather.
An Invercargill police spokesman said the people on board the catamaran, understood to be the Charlie Cat, had been retrieving cray pots about 11am on Saturday when the boat's steering failed and the vessel began taking on water.
The skipper called a nearby fishing boat for help while all on board prepared to abandon the boat.
Five people managed to get into a lifeboat while the remaining three swam to shore.
Te Anau fisherman Bruce Gordon, skipper of the commercial crayfishing boat KCee, responded to the call within 15 minutes, picking up all eight people from rocks.
Mr Gordon's wife Natasha said her husband took the group to Deep Cove before returning to Thompson Sound, hoping to locate the boat, which sank rapidly off Pack Point.
Maritime New Zealand spokeswoman Sophie Hazlehurst said it was aware of the incident and was making preliminary inquiries. A decision whether a full investigation would be launched would be made within a week.