KEY POINTS:
Environment Southland says a boat carrying 500 litres of diesel which sank in Fiordland yesterday is believed to have gone down in the picturesque Acheron Passage.
Acheron Passage, between Dusky Sound and Breaksea Sound, is close to an area described as one of Fiordland's "China shops".
China shop is the term used to describe small discreet areas noted for the abundance or diversity of animal communities, or the abundance of a particular animal species.
The Acheron Passage is also close to Wet Jacket Arm, which boasts the largest densities of black coral in Fiordland.
A helicopter carrying staff from Environment Southland and the Department of Conservation was flying out this morning to assess the area where the vessel Faith went down.
Four men were rescued after the boat hit something underwater shortly before 5pm yesterday.
Sergeant Tod Hollebon, of Te Anau, said a message was heard on the Bluff fisherman's radio about 4.45pm saying Faith was sinking.
Faith is a kauri hulled 14m former fishing trawler weighing about 25 tonnes, Mr Hollebon said.
It was now privately owned, and was yesterday being used by a hunting party. The four men were aged between 16 and 71, he said.
The group managed to get to shore in a dinghy, and tried to save the boat by tying it to trees on the banks of the fiord.
However, it sunk in between 15 and 20 minutes, Mr Hollebon said.
Two other vessels came to the group's rescue and the men were safely helicoptered out to Te Anau last night.
It was most likely the boat had hit rocks, although that had not yet been established. There was no suggestion the men were not operating the boat correctly.
"There's always inherent risk," Mr Hollebon said.
Police would not be investigating the accident.
Regional on-scene commander Warren Tuckey said a helicopter carrying trained oil spill response staffers and a DOC representative would complete a visual assessment of the site and obtain GPS coordinates to pinpoint the vessel's exact location.
There has been some confusion over exactly where the trawler went down.
"It is believed the vessel went down in the Acheron Passage, close to an area deemed to be of special environmental significance," Mr Tuckey said.
What further action was needed would be decided following the aerial assessment, he said.
Southland harbourmaster Kevin O'Sullivan said there had been no reports of any leaked diesel.
It was too early to say what wildlife was potentially affected, as it would depend on where the boat had sunk.
- NZPA